Hypothalamic Releasing Hormone Research Articles

Perinatal exposure to Aroclor 1254 disrupts thyrotropin-releasing hormone mRNA expression in the paraventricular nucleus of male and female rats

Polychlorinated biphenyls (PCBs) are industrial pollutants that act as endocrine disruptors and alter thyroid function. However, it is still unclear whether PCBs can affect hypothalamic thyrotropin releasing hormone (Trh) mRNA expression through TH signaling disruption. As salt-loading dehydration induces tertiary hypothyroidism in the hypothalamic parvocellular paraventricular nuclei (paPVN), and perinatal exposure to Aroclor 1254 (A1254) disrupts the hydric balance in rats, we hypothesized that TRH synthesis could be altered during dehydration in TRH neurons that control the hypothalamic–pituitary–thyroid (HPT) axis activity in rats perinatally exposed to A1254. We examined Trh mRNA expression in the paPVN and the response to salt-loading dehydration (hyperosmotic (hyper) stress) in the progeny of Wistar pregnant rats receiving 0 mg/kg BW (control) or 30 mg/kg BW A1254 daily from gestational days 10–19. Three-month-old offspring were subjected to normosmotic or hyper conditions and Trh mRNA, glucocorticoid receptor (GR) mRNA expression were measured in the PVN by RT-PCR. TRH mRNA and TRH+ neurons were measured in the paPVN by fluorescent in situ hybridization (FISH). As expected, Trh mRNA levels were decreased in the paPVN of male and female rats in the hyper group. Basal Trh mRNA expression and serum TSH were decreased in male rats in the A1254 group. Notably, Trh mRNA levels were further decreased in the paPVN of male and female A1254 + hyper rats, in which the GR mRNA expression was significantly decreased. These results support the hypothesis that perinatal exposure to A1254 results in inadequate adaptive response of the HPT axis in adulthood and contributes to dysregulation of the HPT axis response to salt-loading dehydration.

Association between Intracellular Calcium Signaling and Tumor Recurrence in Human Non-Functioning Pituitary Adenomas.

Clinically non-functioning pituitary adenomas (CNFPAs) are the second most frequent sellar tumor among studies on community-dwelling adults. They are characterized by the absence of hormonal hypersecretion syndrome, and patients present with compressive symptoms, such as a headache and visual field defects. Immunohistochemically, most CNFPAs are of gonadotrope differentiation, with only a few of them being truly null cell adenomas. Although these tumors express receptors for one or more hypothalamic releasing hormones, to what extent this has an impact on the biological and clinical behavior of these neoplasms remains to be defined. In this research, we evaluated the basal and hypothalamic secretagogue-stimulated intracellular calcium mobilization in 13 CNFPAs, trying to correlate this response to the phenotypic features of the patients. Our results indicate that the recurrence of a CNFPA correlates positively with cellular responsiveness, as measured by spontaneous intracellular calcium activity and the ability to respond to multiple hypothalamic secretagogues. We conclude that this finding may be a useful tool for predicting the clinicopathologic behavior of CNFPAs, by testing the variation of cellular responsiveness to hypothalamic secretagogues.

Hypothalamic corticotrophin releasing hormone neurons in stress-induced psychopathology: Revaluation of synaptic contributions.

Stress has a strong influence on mental health around the world. Decades of research has sought to identify mechanisms through which stress contributes to psychiatric disorders such as depression, to potentially guide the development of therapeutics targeting stress systems. The hypothalamic pituitary adrenal (HPA) axis is the key endocrine system that is responsible for coordinating body-wide changes that are necessary for survival under stress, and much of the research aimed at understanding the mechanisms by which stress contributes to depression has focussed on HPA axis dysfunction. Corticotrophin releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) sit at the apex of the HPA axis, integrating signals relevant to stress and external threats, to ensure HPA axis activity is appropriate for the given context. In addition to this, emerging research has demonstrated that neural activity in PVNCRH neurons regulates stress related behaviours via modulation of downstream synaptic targets. This review will summarize convergent evidence from preclinical studies on chronic stress and clinical research in mood disorders demonstrating changes in PVNCRH neural function, consider how this may influence synaptic targets of PVNCRH neurons, and discuss the potential role of these PVNCRH synaptic pathways in the development of maladaptive behaviours following chronic stress that are relevant to depression. We will also highlight important questions for future research aimed at precisely dissecting endocrine and synaptic roles of PVNCRH neurons in chronic stress, their potential interactions, and therapeutic opportunities for the treatment of stress related disorders.

Protective Role and Functional Engineering of Neuropeptides in Depression and Anxiety: An Overview.

Behavioral disorders, such as anxiety and depression, are prevalent globally and touch children and adults on a regular basis. Therefore, it is critical to comprehend how these disorders are affected. It has been demonstrated that neuropeptides can influence behavior, emotional reactions, and behavioral disorders. This review highlights the majority of the findings demonstrating neuropeptides' behavioral role and functional engineering in depression and anxiety. Gut-brain peptides, hypothalamic releasing hormone peptides, opioid peptides, and pituitary hormone peptides are the four major groups of neuropeptides discussed. Some neuropeptides appear to promote depression and anxiety-like symptoms, whereas others seem to reduce it, all depending on the receptors they are acting on and on the brain region they are localized in. The data supplied here are an excellent starting point for future therapy interventions aimed at treating anxiety and depression.

RF34 | PMON222 Reproductive Hormone Secretion is Increased by Intranasal Kisspeptin in Humans

Abstract Background Kisspeptin is a critical activator of hypothalamic gonadotrophin releasing hormone (GnRH) neurons and has significant potential to treat common reproductive disorders. To date, kisspeptin has solely been administered to humans via the intravenous or subcutaneous routes, however intranasal administration could offer a novel non-invasive delivery route, which is preferred by patients. We therefore sought to determine the effects of intranasal kisspeptin on reproductive hormone release in humans for the first time. Methods Randomised, double-blinded, placebo-controlled, cross-over study in 12 healthy men (mean±SEM age 28.3±1.7 yrs; BMI 24.5±0.7 kg/m2). After monitored self-administration of intranasal kisspeptin-54 (3.2, 6.4, 12.8 and 25.6 nmol/kg) or 0.9% saline, serum reproductive hormone levels were measured every 15 minutes for four hours. Subsequently, four women (mean age 29.8±3.7 yrs; BMI 21.2±1.1 kg/m2) with hypothalamic amenorrhoea (HA) attended for the same protocol comparing intranasal kisspeptin-54 (12.8 nmol/kg) and 0.9% saline. Mean ±SEM was presented unless otherwise stated. Time profiles of hormone levels during the four-hour study were compared using two-way ANOVA with Bonferroni's multiple comparison test. Multiple means were compared using one-way ANOVA with Bonferroni's multiple comparison test. Results In healthy men, intranasal kisspeptin dose-dependently increased mean luteinising hormone (LH) levels at doses between 3.2-12.8 nmol/kg (p=0.008 and <0.0001 for 6.4 and 12.8 nmol/kg vs saline, respectively), with the maximal rises occurring at 30-45 minutes post-administration. Correspondingly, the area under the curve (AUC) for the LH change was significantly elevated following all doses of kisspeptin compared to saline (saline: -25.4±70.5 h.IU/L; 3.2 nmol/kg: 172.2±64.2 h.IU/L [p=0.03]; 6.4 nmol/kg: 300.2±79.2 h.IU/L [p=0.002]; 12.8 nmol/kg: 595.7±98.3 h.IU/L [p=0.001]; 25.6 nmol/kg: 549.0±108.6 h.IU/L [p<0.0001]). Follicle stimulating hormone (FSH) levels followed a similar trajectory to LH in response to intranasal kisspeptin. Moreover, kisspeptin at 12.8 nmol/kg increased serum testosterone from 120 minutes onwards (p=0.02), with a maximal change from baseline of 4.9±0.7 nmol/L (p=0.03). In women with HA, intranasal kisspeptin increased mean LH (p=0.002 vs saline), with the peak levels occurring at 30-45 minutes post-administration. The AUC for the LH change was 508.4±77.5 h.IU/L (p=0.02 vs saline AUC for LH). The maximal LH change from baseline was 4.1±0.9 IU/L compared to 0.2±0.4 IU/L for saline (p=0.03). Intranasal kisspeptin increased mean FSH (p=0.01 vs saline). No significant changes in downstream serum oestradiol or progesterone were observed during the acute four-hour study. Conclusion We report the first investigation of the effects of intranasal kisspeptin delivery on reproductive hormone release in humans. Our results demonstrate that intranasal kisspeptin robustly and dose-dependently stimulates reproductive hormone release in healthy men and crucially in a patient-group of women with hypogonadism. Given the ongoing development of kisspeptin therapeutics, intranasal kisspeptin therefore offers a novel, safe, effective and non-invasive route of administration for the management of reproductive disorders. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m., Monday, June 13, 2022 12:36 p.m. - 12:41 p.m.

PMON104 Sellar Gangliocytoma-Pituitary Neuroendocrine Tumor (PitNET) Presenting As Acromegaly

Abstract Growth hormone (GH)-secreting pituitary neuroendocrine tumors (PitNET) arising from somatotrophs is the most common cause of acromegaly. It may rarely develop in the setting of a growth hormone-secreting PitNET associated with a neuronal tumor composed of neoplastic ganglion cells, the so-called mixed gangliocytoma somatotroph PitNET. We present a case of acromegaly which proved to be due to a mixed gangliocytoma somatotroph PitNET on pathology.A 58-year-old, healthy woman presented to the ER with a 3-day history of left-sided vision loss and worsening headache. MRI revealed 4.5×4.2×3.8 cm heterogeneously enhancing bilobed mass consistent with a pituitary PitNET with suprasellar extension causing compression of the optic chiasm, invasion into the left cavernous sinus and partial encasement of the left internal carotid artery. She had coarse facial features, wide feet, multiple skin tags, and a history of multiple colonic polyps. Biochemical work up revealed an IGF-I of 664 ng/ml (50-317), AM cortisol 19.7 mg/dl, ACTH 30 pg/ml, prolactin 15.5 ng/ml, FSH 35.6 mIU/ml, LH 11.3 mIU/ml, and FT4 0.7 ng/dl (0.70-1.48). She underwent endoscopic transsphenoidal resection of the tumor. Histopathology demonstrated mature ganglion cells with neuropil-like areas, intermixed with small cell components. The neuronal population was immunopositive for NeuN (Neuronal nuclei antibody), synaptophysin, and NF (Neurofilament). PitNET cells were positive for GH, prolactin, Pit- 1 transcription factor and the somatostatin 5 receptor, histological features consistent with mixed gangliocytoma and sparsely granulated somatotroph pitNET. Some ganglion cells also showed weak immunostaining with Pit-1. A 3-month follow-up MRI showed a residual 3 cm lesion. IGF-I improved but was still elevated at 456 ng/ml associated with a GH 2.9 ng/ml. Medical treatment with pasireotide was recommended, but the patient temporarily declined further treatment to explore other options with her Naturopath.Gangliocytomas are a rare, benign, slow-growing, differentiated form of neuroblastic tumors of sympathetic nerve fibers, largely extracranial and rarely present in the sellar region, most frequently in association with a PitNET, forming the so-called mixed gangliocytoma PitNET. Definitive diagnosis is established by histological and immunohistochemical studies. Though PitNET components of mixed gangliocytoma PitNET are known to frequently secrete an excess hormone, the ganglionic components also show immunoreactivity for hypothalamic releasing hormones along with other neuroendocrine markers. The histological origin of these mixed tumors is controversial, but the small population of ganglionic cells that express the acidophilic lineage transcription factor, Pit-1, favors the theory of transdedifferentiation of neuroendocrine cells into neuronal elements. Treatment of mixed gangliocytoma- PitNET is similar to other PitNETs and the presence of neural components does not modify aggressiveness or risk of recurrence after surgical resection, as gangliocytomas have a low proliferative index. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Peptide Hormones in Medicine: A 100-Year History

This review is devoted to the 100-year history of the investigation of peptide hormones and the creation of drugs on their basis, starting from the insulin discovery and its introduction into a medical practice in 1921. The basic groups of the peptide hormones are discussed: neurohypophyseal hormones, hypothalamic releasing hormones, incretins, insulin, adrenocorticotropic hormone (ACTH), and calcitonin. The first therapeutic agents based on the peptide hormones were created by a traditional approach that involved the isolation of peptides from animal tissues, their purification to individual compounds, determination of their primary structure, their chemical synthesis or their deep purification, and the creation of a pharmaceutical substance. A modern approach to creation of peptide hormone drugs is based on their consideration as ligands of the corresponding cellular receptors and the use of computer modeling, efficient synthesis methods, and high-throughput screening. The combination of these methods enabled the development of analogs which would be more active than the corresponding natural compounds, exhibit other activities in addition to the hormonal regulation, and be resistant to biodegradation. Such therapeutic agents have been designed on the basis of agonistic and antagonistic analogs of somatostatin and luliberin, and have found wide application in hormonal regulation and cancer treatment. Over the past two decades, the glucagon-like peptide (GLP-1) has been intensively investigated as a potential therapeutic agent. In our review, we describe modifications which resulted in the most highly effective long-acting drugs. Now, natural hormones and their analogs are widely present in the pharmaceutical market.

Postpartum maternal exposure to predator odor alters offspring antipredator behavior, basal HPA axis activity and immunoglobulin levels in adult Brandt’s voles

Predation risk can program offspring behavior, physiology, and fitness through maternal effect, but most studies have mainly focused on this effect during pregnancy; little is known about the effect of postpartum predation risk on offspring’s phenotype. Here, we compared the antipredator behaviors of adult offspring (approximately 90 days old) produced by female Brandt’s voles (Lasiopodomys brandtii) exposed to one of three treatments: cat odor (CO), rabbit odor (RO), and distilled water (DW) for 60 min daily from postpartum day 1–18. Basal levels of plasma adrenocorticotropic hormone (ACTH) and corticosterone (CORT), hypothalamic corticotrophin releasing hormone (CRH), as well as spleen immunoglobulins (IgA, IgM, and IgG) were also measured. Our data showed that the offspring of CO-exposed mothers displayed less head-out behavior to acute 15-min CO exposure, and female offspring showed more freezing behavior. CO offspring showed significantly lower basal ACTH and CORT levels than the RO and DW offspring. Additionally, female but not male CO offspring had higher hypothalamic CRH expression and spleen IgG levels than controls, showing a sex-specific effect. These findings demonstrate that postpartum maternal predator risk exposure promotes a passive-avoidant response to these cues in adult offspring, showing a cross-generational maternal effect of postpartum predation risk. Further, these changes may be associated with alterations in the hypothalamic-pituitary-adrenal axis and immune function.

A Body Weight Sensor Regulates Prepubertal Growth via the Somatotropic Axis in Male Rats.

In healthy conditions, prepubertal growth follows an individual specific growth channel. Growth hormone (GH) is undoubtedly the major regulator of growth. However, the homeostatic regulation to maintain the individual specific growth channel during growth is unclear. We recently hypothesized a body weight sensing homeostatic regulation of body weight during adulthood, the gravitostat. We now investigated if sensing of body weight also contributes to the strict homeostatic regulation to maintain the individual specific growth channel during prepubertal growth. To evaluate the effect of increased artificial loading on prepubertal growth, we implanted heavy (20% of body weight) or light (2% of the body weight) capsules into the abdomen of 26-day-old male rats. The body growth, as determined by change in biological body weight and growth of the long bones and the axial skeleton, was reduced in rats bearing a heavy load compared with light load. Removal of the increased load resulted in a catch-up growth and a normalization of body weight. Loading decreased hypothalamic growth hormone releasing hormone mRNA, liver insulin-like growth factor (IGF)-1 mRNA, and serum IGF-1, suggesting that the reduced body growth was caused by a negative feedback regulation on the somatotropic axis and this notion was supported by the fact that increased loading did not reduce body growth in GH-treated rats. Based on these data, we propose the gravitostat hypothesis for the regulation of prepubertal growth. This states that there is a homeostatic regulation to maintain the individual specific growth channel via body weight sensing, regulating the somatotropic axis and explaining catch-up growth.

Imaging of Endoplasmic Reticulum Ca2+ in the Intact Pituitary Gland of Transgenic Mice Expressing a Low Affinity Ca2+ Indicator.

The adenohypophysis contains five secretory cell types (somatotrophs, lactotrophs, thyrotrophs, corticotrophs, and gonadotrophs), each secreting a different hormone, and controlled by different hypothalamic releasing hormones (HRHs). Exocytic secretion is regulated by cytosolic Ca2+ signals ([Ca2+]C), which can be generated either by Ca2+ entry through the plasma membrane and/or by Ca2+ release from the endoplasmic reticulum (ER). In addition, Ca2+ entry signals can eventually be amplified by ER release via calcium-induced calcium release (CICR). We have investigated the contribution of ER Ca2+ release to the action of physiological agonists in pituitary gland. Changes of [Ca2+] in the ER ([Ca2+]ER) were measured with the genetically encoded low-affinity Ca2+ sensor GAP3 targeted to the ER. We used a transgenic mouse strain that expressed erGAP3 driven by a ubiquitous promoter. Virtually all the pituitary cells were positive for the sensor. In order to mimick the physiological environment, intact pituitary glands or acute slices from the transgenic mouse were used to image [Ca2+]ER. [Ca2+]C was measured simultaneously with Rhod-2. Luteinizing hormone-releasing hormone (LHRH) or thyrotropin releasing hormone (TRH), two agonists known to elicit intracellular Ca2+ mobilization, provoked robust decreases of [Ca2+]ER and concomitant rises of [Ca2+]C. A smaller fraction of cells responded to thyrotropin releasing hormone (TRH). By contrast, depolarization with high K+ triggered a rise of [Ca2+]C without a decrease of [Ca2+]ER, indicating that the calcium-induced calcium-release (CICR) via ryanodine receptor amplification mechanism is not present in these cells. Our results show the potential of transgenic ER Ca2+ indicators as novel tools to explore intraorganellar Ca2+ dynamics in pituitary gland in situ.

Chapter 29 - Endocrine interventions in the intensive care unit

Following the onset of any life-threatening illness that requires intensive medical care, alterations within the neuroendocrine axes occur which are thought to be essential for survival, as they postpone energy-consuming anabolism, activate energy-producing catabolic pathways, and optimize immunological and cardiovascular functions. The hormonal changes present in the acute phase of critical illness at least partially resemble those of the fasting state, and recent evidence suggests that they are part of a beneficial, evolutionary-conserved adaptive stress response. However, a fraction of patients who survive the acute phase of critical illness remain dependent on vital organ support and enter the prolonged phase of critical illness. In these patients, the hypothalamic-pituitary-peripheral axes are functionally suppressed, which may have negative consequences by which recovery may be hampered and the risk of morbidity and mortality in the long-term increased. Most randomized controlled trials of critically ill patients that investigated the impact on the outcome of treatment with peripheral hormones did not reveal a robust morbidity or mortality benefit. In contrast, small studies of patients in the prolonged phase of critical illness documented promising results with the infusion of hypothalamic-releasing hormones. The currently available data corroborate the need for well-designed and adequately powered RCTs to further investigate the impact of these releasing factors on patient-centered outcomes.

Phoenixin(smim20), a gene coding for a novel reproductive ligand, is expressed in the brain of adult zebrafish

Gonadotropin-releasing hormone (GnRH) is a highly conserved neuroendocrine decapeptide that is essential for the onset of puberty and the maintenance of the reproductive state. In addition to its role as hypothalamic releasing hormone, GnRH has multiple functions including modulator of neural activity within the nervous system and of resulting behaviors. These multiple functions are reflected by the existence of multiple isoforms. Despite its importance as a critical hypothalamic releasing hormone, the gnrh1 gene has been lost in zebrafish, and its reproductive function is not compensated for by other GnRH isoforms (GnRH2 and GnRH3), suggesting that, surprisingly, zebrafish do not use any of the GnRH peptides to control reproduction and fertility. Previously we proposed that Phoenixin/SMIM20, a novel peptide identified in mammals and the ligand for the orphan GPR173, is a potential candidate to control the initiation of sexual development and fertility in the zebrafish. Here we confirm the sequence of the zebrafish phoenixin/smim20 gene and by RT-PCR show that it is expressed early in development through adulthood. Subsequently we show that phoenixin/smim20 is expressed in the adult brain including the regions of the hypothalamus important in the control of fertility and reproduction.

Chronic exposure to low dose of bisphenol A causes follicular atresia by inhibiting kisspeptin neurons in anteroventral periventricular nucleus in female mice

Bisphenol-A (BPA) is an estrogenic chemical extensively used in industrial and household applications. The present study was conducted to investigate the effect of chronic exposure to BPA on the adult female neuroendocrine system. Herein, we found that expose of adult female mice to BPA (50 μg/kg) by oral gavage for 60 days (BPA mice) prolonged diestrus and decreased serum 17β-estradiol (E2) concentration by reducing the number of antral follicles and corpora luteum. In comparison with controls, the levels of serum luteinizing hormone (LH), follicle stimulating hormone (FSH), hypothalamic gonadotrophin releasing hormone (GnRH) and the expression of kisspeptin in anteroventral periventricular nucleus (AVPV) decreased in BPA mice, which could be reversed by injecting kisspeptin-10 (i.c.v.). Treatment with BPA or estrogen receptor α (ERα) antagonist MPP, but not ERβ antagonist PHTPP inhibited E2-induced AVPV-kisspeptin expression in ovariectomized mice. Use of ERα agonist PPT rather than ERβ agonist DPN enhanced AVPV-kisspepetin expression, which decreased after treatment with BPA. The amplitude of the proestrus LH surge decreased in mice exposed to BPA, but was recovered by administering kisspeptin-10. The present study provides in vivo evidence that chronic exposure to a low dose of BPA suppressed ERα-induced activation of AVPV-kisspeptin neurons, leading to prolonged diestrus and reduced ovulation in adult female mice.

Multigormonal secretory activity of cells of clinically non-functioning pituitary tumors in vitro and the effect of tyroliberin on it

Experiments on cell cultures demonstrated that isolated cells of clinically inert pituitary tumors release several hormones in small amounts into the medium: luteinizing and follicle-stimulating hormones, alpha-subunit of glycoprotein hormones, prolactin, and growth hormone. Multihormonal secretion of these cells indicates their poor morphofunctional differentiation. In contrast to normal pituitary cells, cells of clinically inert pituitary tumors respond nonspeciflcally to hypothalamic thyrotropin releasing hormone: by increased secretion of prolactin, gonadotropins, glycoprotein hormone alpha-subunit, and growth hormone. This capacity of tumor cells detected in vitro agrees with the probability of increased levels of gonadotropins and glycoprotein hormone alpha-subunit in the serum of patients with clinically inert pituitary tumors during pharmacodynamic thyrotropin releasing hormone test.

Age effect on thyroid hormone brain response in male mice

Thyroid hormones (TH) are important for brain development and central nervous system (CNS) function. Disturbances of thyroid function occur with higher prevalence in the ageing population and may negatively impact brain function. We investigated the age impact on behavior in young adult and old male mice (5 vs. 20 months) with chronic hypo- or hyper-thyroidism as well as in sham-treated controls. Expression of TH transporters and TH responsive genes was studied in CNS and pituitary by in situ hybridization and qRT-PCR, whereas TH serum concentrations were determined by immunoassay. Serum TH levels were lower in old compared with young hyperthyroid mice, suggesting a milder hyperthyroid phenotype in the aged group. Likewise, elevated plus maze activity was reduced in old hyperthyroid animals. Under hypothyroid conditions, thyroxine serum concentrations did not differ in young and old mice. Both groups showed a comparable decline in activity and elevated anxiety levels. However, an attenuated increase in hypothalamic thyrotropin releasing hormone and pituitary thyroid stimulating hormone transcript expression was found in old hypothyroid mice. Brain expression of monocarboxylate transporter 8 and organic anion transporting polypeptide 1c1 was not affected by age or TH status. In summary, ageing attenuates neurological phenotypes in hyperthyroid but not hypothyroid mice, which fits with age effects on TH serum levels in the animals. In contrast no changes in TH transporter expression were found in aged mouse brains with hyper- or hypo-thyroid state.

SUN-403 Drinking Water from a Dirty Prison Sink: A Rare Case of Acute Myeloid Leukemia with Diabetes Insipidus and Panhypopituitarism

Panhypopituitarism is an extremely rare disorder in acute myeloid leukemia (AML) with only 6 cases previously reported to date. The mechanism of AML causing panhypopituitarism is unclear, but some of the leading hypotheses support leukemic infiltration or leukostasis. A 30-year-old incarcerated woman with a history of intravenous drug use and hepatitis C presented with 5 days of fevers, vomiting, and progressive abdominal pain. She reported an unintentional 30 lb weight loss and a month of polyuria and polydipsia severe enough to cause her to drink water from the dirty sink in her prison cell. Patient denied headache, visual disturbance, or galactorrhea. Initial laboratory studies showed a white blood cell count of 350K with 90% myeloblasts, consistent with AML. She received emergent leukocytapheresis and was started on cytarabine and daunorubicin chemotherapy. Upon admission, she was also noted to have hypernatremia (Na 152 mmol/L), persistent hypotension (BP 80s/40s) unresponsive to fluid resuscitation, and high urine output of 5-14 L/day. Desmopressin (DDAVP) 4 mcg IV was administered and resulted in increased urine osmolality from 116 to 451 mOsm/L with significant decrease in urine output, consistent with central diabetes insipidus (cDI). Brain MRI showed heterogeneous thickening of the infundibulum and an absence of the posterior pituitary T1 bright spot, which can be seen in cDI. Hormonal evaluation revealed low free T4 0.77 ng/dL (ref. 0.93-1.70) and normal TSH 4.03 mIU/mL (ref. 0.27-4.20), consistent with central hypothyroidism. Prolactin was mildly elevated at 39 ng/mL (ref. 4.8-23.3). She was also noted to have low AM cortisol 3 µg/dL (ref. 5-20) prompting a cosyntropin stimulation test which showed baseline cortisol of 5.9 rising to 13.2 µg/dL, which is an inadequate response. She was treated for panhypopituitarism with hydrocortisone 50 mg IV Q8H tapered gradually to a replacement dose, DDAVP 50 mcg PO QHS, and levothyroxine 50 mcg PO daily. Her remaining hospital course was complicated by neutropenic fever. She was ultimately transferred to Massachusetts General Hospital on hospital day 19 (Day 16 of chemotherapy) to be closer to her family. This is a rare case report of a young patient with new diagnosis of AML presenting with both cDI and panhypopituitarism. The mechanism remains unclear. One possible rationale is pituitary stalk involvement by leukemic infiltration which is evidenced by a thickening appearance on MRI. Another explanation is an ischemic or thrombotic effect related to hyperleukocytosis. The resulting hyperviscosity and subsequent disruption of hypophyseal portal capillary flow can impede release of hypothalamic hormones destined for the pituitary. Our patient had MRI findings of an abnormally thickened stalk and lack of “bright spot” which supports the hypothesis of leukemic infiltration and significant disruption of the hypothalamic-pituitary axes.

Neuroendocrinology of reproduction: Is gonadotropin-releasing hormone (GnRH) dispensable?

Gonadotropin releasing hormone (GnRH) is a highly conserved neuroendocrine decapeptide that is essential for the onset of puberty and the maintenance of the reproductive state. First identified in mammals, the GnRH signaling pathway is found in all classes of vertebrates; homologues of GnRH have also been identified in invertebrates. In addition to its role as a hypothalamic releasing hormone, GnRH has multiple functions including modulating neural activity within specific regions of the brain. These various functions are mediated by multiple isoforms, which are expressed at diverse locations within the central nervous system. Here we discuss the GnRH signaling pathways in light of new reports that reveal that some vertebrate genomes lack GnRH1. Not only do other isoforms of GnRH not compensate for this gene loss, but elements upstream of GnRH1, including kisspeptins, appear to also be dispensable. We discuss routes that may compensate for the loss of the GnRH1 pathway.

Nitric oxide acutely modulates hypothalamic and neurohypophyseal carbon monoxide and hydrogen sulphide production to control vasopressin, oxytocin and atrial natriuretic peptide release in rats.

Nitric oxide (NO) negatively modulates the secretion of vasopressin (AVP), oxytocin (OT) and atrial natriuretic peptide (ANP) induced by the increase in extracellular osmolality, whereas carbon monoxide (CO) and hydrogen sulphide (H2 S) act to potentiate it; however, little information is available for the osmotic challenge model about whether and how such gaseous systems modulate each other. Therefore, using an acute ex vivo model of hypothalamic and neurohypophyseal explants (obtained from male 6/7-week-old Wistar rats) under conditions of extracellular iso- and hypertonicity, we determined the effects of NO (600μmolL-1 sodium nitroprusside), CO (100μmolL-1 tricarbonylchloro[glycinato]ruthenium [II]) and H2 S (10mmolL-1 sodium sulphide) donors and nitric oxide synthase (NOS) (300μmolL-1 Nω -methyl-l-arginine [LNMMA]), haeme oxygenase (HO) (200μmolL-1 Zn(II) deuteroporphyrin IX 2,4-bis-ethylene glycol [ZnDPBG]) and cystathionine β-synthase (CBS) (100μmolL-1 aminooxyacetate [AOA]) inhibitors on the release of hypothalamic ANP and hypothalamic and neurohypophyseal AVP and OT, as well as on the activities of NOS, HO and CBS. LNMMA reversed hyperosmolality-induced NOS activity, and enhanced hormonal release by the hypothalamus and neurohypophysis, in addition to increasing CBS and hypothalamic HO activity. AOA decreased hypothalamic and neurohypophyseal CBS activity and hormonal release, whereas ZnDPBG inhibited HO activity and hypothalamic hormone release; however, in both cases, AOA did not modulate NOS and HO activity and ZnDPBG did not affect NOS and CBS activity. Thus, our data indicate that, although endogenous CO and H2 S positively modulate AVP, OT and ANP release, only NO plays a concomitant role of modulator of hormonal release and CBS activity in the hypothalamus and neurohypophysis and that of HO activity in the hypothalamus during an acute osmotic stimulus, which suggests that NO is a key gaseous controller of the neuroendocrine system.

Store-operated Ca2+ entry and Ca2+ responses to hypothalamic releasing hormones in anterior pituitary cells from Orai1−/− and heptaTRPC knockout mice

Store operated Ca2+ entry (SOCE) is the most important Ca2+ entry pathway in non-excitable cells. However, SOCE can also play a pivotal role in excitable cells such as anterior pituitary (AP) cells. The AP gland contains five different cell types that release six major AP hormones controlling most of the entire endocrine system. AP hormone release is modulated by Ca2+ signals induced by different hypothalamic releasing hormones (HRHs) acting on specific receptors in AP cells. TRH and LHRH both induce Ca2+ release and Ca2+ entry in responsive cells while GHRH and CRH only induce Ca2+ entry. SOCE has been shown to contribute to Ca2+ responses induced by TRH and LHRH but no molecular evidence has been provided. Accordingly, we used AP cells isolated from mice devoid of Orai1 channels (noted as Orai1−/− or Orai1 KO mice) and mice lacking expression of all seven canonical TRP channels (TRPC) from TRPC1 to TRPC7 (noted as heptaTRPC KO mice) to investigate contribution of these putative channel proteins to SOCE and intracellular Ca2+ responses induced by HRHs. We found that thapsigargin-evoked SOCE is lost in AP cells from Orai1−/− mice but unaffected in cells from heptaTRPC KO mice. Conversely, while spontaneous intracellular Ca2+-oscillations related to electrical activity were not affected in the Orai1−/− mice, these responses were significantly reduced in heptaTRPC KO mice. We also found that Ca2+ entry induced by TRH and LHRH is decreased in AP cells isolated from Orai1−/−. In addition, Ca2+ responses to several HRHs, particularly TRH and GHRH, are decreased in the heptaTRPC KO mice. These results indicate that expression of Orai1, and not TRPC channel proteins, is necessary for thapsigargin-evoked SOCE and is required to support Ca2+ entry induced by TRH and LHRH in mouse AP cells. In contrast, TRPC channel proteins appear to contribute to spontaneous Ca2+-oscillations and Ca2+ responses induced by TRH and GHRH. We conclude that expression of Orai1 and TRPC channels proteins may play differential and significant roles in AP physiology and endocrine control.

Spontaneous pregnancy after full recovery from hypopituitarism caused by lymphocytic hypophysitis.

SummaryLymphocytic hypophysitis (LyH) has been known to be associated with pregnancy. We herein report the case of a 33-year-old woman who underwent vaginal delivery without massive bleeding at 40 weeks of gestation. Because of the presence of headache and terrible fatigue after childbirth, she visited our hospital. Severe hyponatremia (Na, 118 mEq/L) and visual field abnormality was noted upon examination. MRI revealed pituitary enlargement with a swollen pituitary stalk, albeit at low signal intensity. Basal pituitary hormone levels were all reduced and remained low after exogenous administration of hypothalamic-releasing hormones. She was diagnosed with LyH and was started on prednisolone 60 mg/day. A month later, her pituitary function had gradually improved together with a decrease in pituitary enlargement and recovery of her visual field. The dose of prednisolone was gradually reduced and finally withdrawn 27 months later. After prednisolone withdrawal, her pituitary function remained normal despite the absence of any hormonal replacement. A year later, she became pregnant without medication and delivered a second baby without LyH recurrence. Thereafter, her pituitary function has been normal for more than 5 years. Two valuable observations can be highlighted from the case. First, the patient completely recovered from LyH through prompt prednisolone therapy during its initial phase and had almost normal pituitary function. Second, after recovery from LyH, she was able to undergo spontaneous pregnancy and deliver a baby. We believe that reporting incidences of spontaneous pregnancy after complete normalization of pituitary function in patients with LyH is of great significance.Learning points:Females are more affected by LyH than males given its strong association with pregnancy.LyH possesses characteristic findings on pituitary MRI.Glucocorticoid therapy for LyH has been recommended as an effective treatment.A history of previous pregnancies does not increase the risk of developing AH in subsequent pregnancies.Early induction of high-dose prednisolone was therapeutically effective in treating LyH.