Hypothalamo-pituitary Axis Research Articles

The vomeronasal organ of the tammar wallaby

The vomeronasal organ is the primary olfactory organ that detects sexual pheromones in mammals. We investigated the anatomy of the vomeronasal organ of the tammar wallaby (Macropus eugenii), a small macropodid marsupial. Pheromones may be important for activation of the hypothalamo-pituitary axis of tammar males at the start of the breeding season because plasma testosterone and luteinizing hormone concentration in males rise concurrently with pregnancy and the post-partum ovulation in females. The gross anatomy and the connection to the brain of the vomeronasal organ were examined by light and electron microscopy in adult male and female tammars. The vomeronasal organ was well developed in both sexes. The vomeronasal organ is a tubular organ connected at the rostral end via the nasopalatine duct (incisive duct) to the mouth and nasal cavity. At the rostral end the lumen of the vomeronasal organ was crescent shaped, changing to a narrow oval shape caudally. Glandular tissue associated with the vomeronasal organ increased towards the blind end of the organ. The tammar has the typical pattern of mammalian vomeronasal organs with electron-dense supporting cells and electron-lucent receptor cells. Microvilli were present on the surface of both epithelia while cilia were only found on the surface of the non-receptor epithelium. Some non-receptor epithelial cells appeared to secrete mucus into the vomeronasal organ lumen. The vomeronasal organ shows a high degree of structural conservation compared with eutherian mammals. The degree of vomeronasal organ development makes it likely that, as in other mammals, pheromones are important in the reproduction of the tammar.

The Gonadotropin-Releasing Hormone Type I Receptor is Expressed in the Mouse Cerebellum

Gonadotropin-releasing hormone (GnRH) is a decapeptide hypothalamic hormone that was named according to its first discovered function--at the head of the neuroendocrine reproductive axis. Numerous other organ systems express GnRH and/or its receptor, although a specific physiological role for GnRH outside of the reproductive axis has yet to be established. Several studies in lower vertebrates have reported GnRH and/or its receptor in the cerebellum. Here, we describe the presence of immunoreactive GnRH receptors in the Purkinje cells of the mammalian cerebellum for the first time. This study provides compelling anatomical evidence for a common link between the cerebellum and the hypothalamo-pituitary axis. Dysfunction of this link occurs in the rare genetic ataxia disorders--Gordon Holmes syndrome and Boucher-Neuhauser syndrome.

Gonadotropin-Releasing Hormone (GnRH) and GnRH Receptor in Bladder Cancer Epithelia and GnRH Effect on Bladder Cancer Cell Proliferation

Introduction: Gonadotropin-releasing hormone (GnRH) is the pivotal hormone in the hypothalamopituitary gonadal axis. Recently, localization of extrahypothalamic GnRHs and GnRH receptors has been made in several organs but not in the bladder. We studied the extrahypothalamic GnRH and GnRH receptor in bladder cancer epithelia, and the role of GnRH on bladder cancer cell proliferation. Material and Methods: Normal human bladder mucosa, human transitional bladder cancer tissue, and 4 bladder cancer cell lines were used. For culture media, normal or charcoal-stripped serum with exogenous GnRH of different concentrations (0, 10^–3, 10^–5, and 10^–7M) were supplemented. For detection of GnRH and the GnRH receptor and its mRNAs, RNase protection assay, in situ hybridization, and immunocytochemistry were performed. Cellular proliferation was measured by hemocytometer and the cell cycle by flow cytometer. Results: GnRH and GnRH receptor mRNA expression were detected in all cancer cell lines and human bladder cancer tissues. GnRH and GnRH receptors were localized in bladder cancer epithelial cells, but the density was not even. There were no significant differences (p > 0.05) in proliferation, and no significant change (p > 0.05) in cell cycle with GnRH supplements compared to controls. Conclusion: The bladder epithelia produce GnRH and the GnRH receptor in both normal and malignant tissues, but GnRH does not induce proliferation or cell cycle change of bladder cancer cells.

Free Cortisol in Sepsis and Septic Shock

Severe sepsis activates the hypothalamopituitary axis, increasing cortisol production. In some studies, hydrocortisone substitution based on an adrenocorticotropic hormone-stimulation test or baseline cortisol measurement has improved outcome. Because only the free fraction of cortisol is active, measurement of free cortisol may be more important than total cortisol in critically ill patients. We measured total and free cortisol in patients with severe sepsis and related the concentrations to outcome. In a prospective study, severe sepsis was defined according the American College of Chest Physicians/Society of Critical Care Medicine criteria. Blood samples were drawn within 24 h of study entry. Serum cortisol was analyzed by electrochemiluminescence immunoassay. The Coolens method was used for calculating serum free cortisol concentrations. Blood samples were collected from 125 patients, of whom 62 had severe sepsis and 63 septic shock. Hospital mortality was 21%. Calculated free serum cortisol correlated well with serum total cortisol (r = 0.90, P < 0.001). There was no difference in the total cortisol concentrations in patients with sepsis and septic shock (728 +/- 386 nmol/L vs 793 +/- 439 nmol/L, P = 0.44). Nonsurvivors had higher calculated serum free (209 +/- 151 nmol/L) and total (980 +/- 458 nmol/L) cortisol concentrations than survivors (119 +/- 111 nmol/L, P = 0.002, and 704 +/- 383 nmol/L, P = 0.002). Depending on the definition, the incidence of adrenal insufficiency varied from 8% to 54%. Clinically, calculation of free cortisol does not provide essential information for identification of patients who would benefit from corticoid treatment in severe sepsis and septic shock.

GnRH or eCG treatment fails to restore reproductive function in GnRH immunized ewes

This study was designed to evaluate the potential of using eCG or GnRH in restoring reproductive functions in GnRH immunized ewes. Thirty-three multiparous Kıvırcık ewes were randomly assigned into either control group ( n = 11) or immunization group ( n = 22). Ewes were immunized against GnRH by injecting with a cocktail of ovalbumin-LHRH-7 (ovalbumin-GnRH-7) and thioredoxin-LHRH-7 (thioredoxin-GnRH-7) fusion proteins generated by recombinant DNA technology in April. 500 IU eCG or 0.008 mg GnRH analogue was used to induce ovulations. Serum GnRH antibodies were present in animals of the immunized group beginning the second week after the first immunization and maintained throughout the study (14 months). Immunization caused anestrus in immunized ewes. eCG or GnRH analogue administration given after 14 days progestagen (20 mg fluorogestone acetate, FGA) treatment during breeding season (mid July) did not induce ovulation in these ewes. Two more attempts with single or multiple eCG injections failed to induce ovulation in this group as well. It appears that the gonadotropin stimulation was not of adequate time since neither eCG nor GnRH administration was able to restore reproductive function in immunized animals. The immunization effect lasted more than a year. These results suggest that GnRH immunization exerts its effect via the hypothalamo-pituitary axis and that more than such stimulation is required to overcome the reproductive suppression.

Chronic headache and pituitary tumors

Pituitary tumors come to clinical attention due to endocrine dysfunction, distortion of local structures surrounding the pituitary fossa, or as an incidental finding during neuroimaging for headache. Explanations for pituitary tumor-associated headache include stretching of the dura mater and invasion of pain-producing structures within the cavernous sinus. However, small functional pituitary lesions may present with severe headache without cavernous sinus invasion or suprasellar extension. Prolactinomas and growth hormone-secreting tumors have a high prevalence of rare headache phenotypes with or without autonomic features, suggesting that biochemical abnormalities within the hypothalamo-pituitary axis may play a role in headache. Somatostatin analogues may be highly effective at aborting headache associated with functionally active pituitary lesions, particularly in the case of acromegaly. A proposed mechanism for this is inhibition of nociceptive peptides. This article summarizes the clinical features, pathophysiology, and potential treatment approaches to pituitary tumor-associated headache.

Place de l’axe corticotrope dans le développement de l’obésité abdominale

Obesity is increasing worldwide. Abdominal obesity, which is due to the development of visceral adipose tissue, leads to metabolic disorders. Because abdominal obesity is associated with Cushing syndrome, many studies have been performed to find out how the hypothalamopituitary adrenal axis is involved in this disorder. Here, we propose to review these data before giving our experience on changes in hypothalamopituitary adrenal axis activity regarding fat mass distribution in prepubertal children.

Aging and hormones of the hypothalamo-pituitary axis: Gonadotropic axis in men and somatotropic axes in men and women

Neuroendocrinology of the aging (male) gonadal and (male and female) somatotropic axes will be reviewed. A companion chapter discusses reproductive hormonal changes in aging women. Both the gonadal and growth-hormone/insulin-like growth factor (GH/IGF-I) axes function as ensembles. The ensembles comprise tripartite interactions among the brain (hypothalamus), anterior pituitary gland (gonadotrope and somatotrope cells) and target organs (testis, liver, muscle, fat and brain). Compelling evidence indicates that combined hypothalamic and gonadal adaptations operate in the reproductive axis of older men, and multiple hypothalamic adaptations prevail in the GH axis of elderly men and women. Evolving investigative methods allow more precise parsing of the particular mechanisms that subserve such age-related changes, and suggest novel interventional strategies to evaluate the physiological impact of the dynamic alterations discerned in aging individuals.

Sleep and musculoskeletal pain

The article focuses on sleep disorders as a risk factor for musculoskeletal pain. It is reported that sleep disorders at baseline predict development of chronic musculoskeletal pain in initially healthy working female and male one year later. Job strain was also predictive of musculoskeletal pain in female. The hypothalamo-pituitary adrenal axis is activated by sleep disturbance which results in elevated cortisol levels.

Endocrine Status and Development of Porcine Testicular Tissues in Host Mice

Clarification of the endocrine status of host mice provides us with basic knowledge with which we can manipulate the growth and function of xenografted testicular tissues. We investigated the hormonal profiles of castrated mice grafted with porcine immature testicular tissues from 30 to 210 or more days after grafting (day 0=castration and grafting). The serum follicle stimulating hormone (FSH) concentrations of the host mice declined (P<0.05) from day 60 compared with those of the castrated, ungrafted mice. The serum inhibin and testosterone levels were higher (P<0.05) than those in the castrated, ungrafted mice from days 30 and 90 days, respectively. The inhibin levels further increased (P<0.05) from day 90, during which time the levels were higher (P<0.05) than those in the intact male mice. In the grafts, formation of lumens occurred in the seminiferous cords on day 90 and spermatozoa appeared in the lumens from day 120. However, spermatogenesis in the grafts did not reach the qualitatively normal levels observed in adult boars. The intensity of the immune reaction to inhibin alpha subunits in the Sertoli cells of the grafts decreased with differentiation of the seminiferous tubules. The present findings indicate that a feedback loop was established between the mouse hypothalamo-pituitary axis and the grafted porcine tissues from 60 days post-grafting. The results also indicate that the serum inhibin levels in the host mice remained high even after the appearance of lumens in the seminiferous tubules of the grafted tissues; this is strikingly different to the situation in normal male animals, in which the serum inhibin levels decline at around the time of tubular differentiation. The lack of efferent ducts in the tubules of the grafted tissues probably caused the accumulation of inhibin to be released into the lumens, resulting in high concentrations of circulating inhibin. These high levels of inhibin may directly affect spermatogenic activity and suppress FSH secretion.

Regulation of NGFI‐B/Nur77 gene expression in the rat ovary and in leydig tumor cells MA‐10

NR4A1, also called NGFI-B in the rat, Nur77 in the mouse and TR3 in humans, belongs to the orphan nuclear steroid hormone receptor superfamily and is one of the immediate-early genes. In the endocrine organs, including the gonads, NGFI-B/Nur77 gene expression is rapidly induced by pituitary hormones. NGFI-B/Nur77 expression was found to be rapidly reduced by an estrogenic endocrine disrupter, diethylstilbestrol (DES) in theca interna cells of immature rat ovaries. DES treatment also triggered a rapid decrease of serum luteinizing hormone (LH) levels, suggesting that DES acts on the hypothalamo-pituitary axis to suppress LH secretion from the pituitary. The transcriptional regulation of NGFI-B/Nur77 by LH/human chorionic gonadotropin (hCG) or 8-bromoadenosine 3'-5'-cyclic monophosphate (8 Br-cAMP) was examined in mouse Leydig tumor cells MA-10. Luciferase assays using NGFI-B/Nur77 promoter constructs and electric mobility shift assays (EMSA) showed that NGFI-B/Nur77 gene expression was mediated through three of the four activator protein-1 (AP-1)-like sites, namely the -233 AP-1, -213 AP-1 and -69 AP-1 sites adjacent to the transcription start site of the NGFI-B/Nur77 promoter. We also demonstrated here that both the Jun family and cAMP-responsive element binding (CREB) proteins bind to the -233 AP-1 site, whereas the main binding protein to the -213 AP-1 site was CREB, and Jun family protein to the -69 AP-1 site, respectively. The rapid induction of NGFI-B/Nur77 gene expression by LH/hCG in MA-10 cells appears to be mediated by both CREB and Jun family proteins through the cAMP-protein kinase A (PKA) pathway.

Feeding affects reproductive performance and reproductive endocrinology in the gilt and sow

The pig is considered to be a highly prolific species with ahigh ovulation rate and if mated at the right moment, thesow also holds a very high probability of pregnancy. It isgenerally accepted that little variation in live weight of thesow throughout the production cycle is associated withhigh fertility and improved longevity. This goal requireshigh energy intake during lactation, which may beachieved by ad libitum feeding with high energy high pro-tein lactation diet without feed restriction, especially dur-ing the last part of lactation. In endocrinological terms,gonadotrophin secretion is affected by suckling and met-abolic messengers, which transfer information regardinglactation and metabolic state of the dam. These messagesare received by the hypothalamo-pituitary axis and even-tually follicular development is either inhibited orencouraged, depending on the messages. Managementpractices such as intermittent suckling are developed toalleviate the sow to meet with the metabolic challengesimposed by lactation and expected fertility. After mating,social stress and restricted feeding may create a situationwhere embryonic survival and pregnancy is jeopardized.The risk of losing embryos/pregnancy may be highestwhen individual sows experience considerable food dep-rivation for longer than two days around implantation.Feeding a sow group more may provide the farmer withsimple solution to problems with early pregnancy.Approaching term, compromising between high birthweigh of newborn piglets associated with abundant feed-ing and a feed restriction together with increase in fiber toimprove intestinal function may be the strategy of choice.

Systemic and endocrine manifestations of Langerhans’ cell histiocytosis: current concepts in diagnosis and management

Langerhans’ cell histiocytosis (LCH) is a rare disease of unknown etiology and variable biologic behavior and course. Almost every organ can be affected; however, it frequently involves the bones, lungs, skin and lymph nodes. LCH exhibits a particular predilection for involvement of the hypothalamo–pituitary axis resulting in diabetes insipidus and/or other anterior pituitary deficiencies. Although LCH can sometimes resolve spontaneously, it usually follows a chronic course and systemic treatment is mandatory for the management of multisystem disease. However, a significant number of patients will develop at least one permanent sequela as a consequence of the disease, with diabetes insipidus being the most common. A multidisciplinary approach is always needed in diagnosis, treatment and follow-up of all patients with LCH.

Differential long-term dietary regulation of adipokines, ghrelin, or corticosterone: impact on adiposity

In the present experiment, we examined in Long-Evans rats the long-term effects of diets that differed in the energy provided by proteins (P) and fats (F) but provided a constant level of energy from carbohydrates (55%) on various hormones regulating feeding and metabolism. Sixty adult rats were fed for 2 months either a high-fat (protein-to-fat, PF 5/40), a control (PF 15/30), low-fat (PF 30/15), or high-protein (PF 40/5) diet ad libitum. Both the PF 30/15 and the PF 40/5 rats ate significantly less than their PF 5/40 and PF 15/30 counterparts throughout the experiment (P<0.001). PF 40/5 rats weighed less than PF 15/30 rats (PL=0.04). PF 40/5 and PF 30/15 rats had smaller epididymal and perirenal adipose tissue depots than PF 5/40 and PF 15/30 rats (P<0.05 or less). Adiponectin (+25-47%) and leptin levels in the PF 5/40 rats were higher than in the three other groups (P<0.0025 or less). Ghrelin concentration in the PF 30/15 group was also higher than in the three other groups (P<0.001 versus PF 5/40; P<0.05 versus PF 15/30 and PF 40/5). Corticosterone level was 2- to 2.5-fold higher in PF 40/5 rats than in the three other groups (P<0.01 or less). Immunoreactive insulin was not different between the four groups. Our current findings thus show that increases in the protein content resulted in a greater degree of leanness, but at sufficiently high levels, also activated the hypothalamo-pituitary axis. Ghrelin appeared to be down-regulated by increases in fat content and no obvious signs of insulin resistance were observed in any of the rats under study.

Comparison of hypothalamopituitary axis dysfunction of intrasellar and third ventricular craniopharyngiomas in children

In this study, we attempted to determine if different locations of a tumor influence the hypothalamopituitary axis function and outcomes with childhood craniopharyngiomas. The preoperative, postoperative, and long-term follow-up endocrinological disturbances of 66 children with a craniopharyngioma were retrospectively studied. The patients were divided into two subgroups according to the location of the tumor (intrasellar and third ventricle floor). The mean age at onset was 8.02 (range, 1.42–17.58) years. These patients were followed-up for a median duration of 7.2 (range, 2–22) years. Vision problems as the first symptom were more common in Group One (with intrasellar tumors) compared to Group Two (55.6% vs 15.4%; p = 0.001; Fisher’s exact test). Increased intracranial pressure was the most common initial symptom in patients in Group Two (51.3%) and the second most common symptom in Group One (37%). The majority of patients in both Group One and Group Two required some forms of pituitary hormone supplements (96% vs 84%). At the last follow-up, more patients with intrasellar craniopharyngiomas needed cortisone supplements (79.2% in Group One vs 45.9% in Group Two; p = 0.016; Fisher’s exact test); however, children with third ventricle floor tumors had more prevalent weight gain (4.2% in Group One vs 27.0% in Group Two; p = 0.038; Fisher’s exact test). There were different initial presentations and endocrinological outcomes between children with intrasellar and third ventricle floor craniopharyngiomas. The intrasellar tumors had greater pituitary hormone disturbance. However, at the long-term follow-up, children with third ventricle floor tumors had a greater prevalence of being overweight and obese, which was associated with hypothalamic dysfunction.

Cutis Laxa Associated with Central Hypothyroidism owing to Isolated Thyrotropin Deficiency in a Newborn

Cutis laxa is an uncommon entity characterized by laxity of the skin, which hangs in loose folds, producing an appearance of premature aging. It can be subdivided into congenital and acquired forms. Genetic forms of cutis laxa include at least three forms of recessive disease, an X-linked form also termed occipital horn syndrome and an autosomal dominant form. Isolated pituitary hormone deficiency can be induced by many causes including mechanical destruction of the hypothalamo-pituitary axis, neoplasm, inflammation, and injury and genetic defects of pituitary hormone production and secretion. Isolated-thyrotropin deficiency has been considered to be a rare disease. We report a newborn with autosomal recessive form of congenital cutis laxa, who had congenital hypothyroidism owing to isolated thyrotropin deficiency. To the best of our knowledge, this is the first instance of this association to be reported in the literature.

Strain differences in anxiety-like behavior: Association with corticotropin-releasing factor

The purpose of the current study was to relate basal corticotropin-releasing factor (CRF) mRNA level in the central nucleus of the amygdala (CeA) with anxiety-like behavior using three strains of rat reported to exhibit a range of behavioral and neuroendocrine responses to stress. Anxiety-like behavior was determined for Fischer (F344), Wistar, and Wistar-Kyoto (WKY) rats with an elevated plus-maze and CRF mRNA level was measured using in situ hybridization. WKY rats exhibited more anxiety-like behavior on the elevated plus-maze than both F344 ( p's < 0.01) and Wistar rats ( p's < 0.05). WKY rats had higher basal levels of CRF mRNA in the CeA than F344 rats ( p < 0.05) with a trend toward higher levels than Wistar rats ( p = 0.06). Wistar rats had similar indices of anxiety with F344 rats and comparable levels of CRF mRNA in the CeA. Basal plasma corticosterone was similar for all three strains and repeated experience with the plus-maze had no effect on basal corticosterone levels or CRF mRNA levels in the paraventricular nucleus of the hypothalamus (PVN) for Wistar or WKY rats. Consistent with reported hyperactivity of the hypothalamopituitary adrenal axis of F344 rats with repeated stress, we observed elevated corticosterone following repeated exposure to the elevated plus-maze in F344 rats ( p < 0.01) with a trend toward increased CRF mRNA levels in the PVN ( p = 0.09). Heightened expression of CRF in the CeA of WKY rats may be involved in anxiety-like behaviors observed in this strain.

Pituitary abnormalities in Prader–Willi syndrome and early onset morbid obesity

Prader-Willi syndrome (PWS) is a well-defined syndrome of childhood-obesity which can serve as a model for investigating early onset childhood obesity. Many of the clinical features of PWS (e.g., hyperphagia, hypogonadotropic hypogonadism, growth hormone deficiency) are hypothesized to be due to abnormalities of the hypothalamus and/or pituitary gland. Children who become severely obese very early in life (i.e., before age 4 years) may also have a genetic etiology of their obesity, perhaps with associated neuroendocrine and hypothalamo-pituitary defects, as infants and very young children have limited access to environmental factors that contribute to obesity. We hypothesized that morphologic abnormalities of the pituitary gland would be seen in both individuals with PWS and other subjects with early onset morbid obesity (EMO). This case-control study included individuals with PWS (n = 27, age 3 months to 39 years), patients with EMO of unknown etiology (n = 16, age 4-22 years; defined as body mass index greater than the 97th centile for age before age 4 years), and normal weight siblings (n = 25, age 7 months to 43 years) from both groups. Participants had 3-dimensional magnetic resonance imaging to evaluate the pituitary gland, a complete history and physical examination, and measurement of basal pituitary hormones. Subjects with PWS and EMO had a higher prevalence of pituitary morphological abnormalities than did control subjects (74% PWS, 69% EMO, 8% controls; P < 0.001). Anterior pituitary hormone deficiencies were universal in individuals with PWS (low IGF-1 in 100%, P < 0.001 PWS vs. controls; central hypothyroidism in 19%, P = 0.052, and hypoplastic genitalia or hypogonadotropic hypogonadism in 100%, P < 0.001), and was often seen in individuals with EMO (6%, P = 0.89 vs. control, 31%, P = 0.002, and 25%, P = 0.018, respectively). The presence of a hypoplastic pituitary gland appeared to correlate with the presence of anterior pituitary hormone deficiencies in individuals with EMO, but no correlation was apparent in individuals with PWS. In conclusion, the high frequency of both morphological and hormonal abnormalities of the pituitary gland in both individuals with PWS and EMO suggests that abnormalities in the hypothalamo-pituitary axis are features not only of PWS, but also frequently of EMO of unknown etiology.

Neuroendocrine dysfunction after aneurysmal subarachnoid hemorrhage – need for reassessment even years after the hemorrhage?

Objectives: There has been increasing evidence for neuroendocrine dysfunction as a sequel of aneurysmal subarachnoid hemorrhage (SAH). However, only one recent investigation has assessed pituitary function in SAH-survivors in a longitudinal design 3 and 12 months after the hemorrhage, but nothing is known about the dynamics of the hypothalamo-pituitary axis in the years following the bleeding.

The Diagnosis of Partial Growth Hormone Deficiency in Adults with a Putative Insult to the Hypothalamo-Pituitary Axis

Similar to patients with severe GH deficiency (GHD), those with a more moderate impairment of GH secretion [GH insufficiency (GHI)] have abnormal body composition, dyslipidemia, and insulin resistance. Given the inherent problems in the diagnosis of severe GHD, the situation is likely to be even more difficult in individuals with GHI. The objective of the study was to examine the utility of GH stimulation tests and GH-dependent proteins in the diagnosis of GHI. The study was a cross-sectional, case-controlled study. The study included 31 patients with GHD, 23 with GHI [peak GH 3-7 microg/liter (9-21 mU/liter)], and 30 age- and sex-matched controls. Demographic and biochemical markers of GH status were measured. Nineteen of the patients with GHI (83%) had no additional anterior pituitary hormone deficits. Ten GHI patients showed discordant GH status based on the two GH stimulation tests performed. GH status was defined by the highest peak GH value achieved; in four this was to the insulin tolerance test (ITT), four the arginine test, and two the GHRH-arginine test. In five of the six patients in whom GH status was not defined by the ITT, peak GH levels to the ITT were in the range 2.4-2.9 microg/liter. IGF-I values for the GHI adults were significantly lower than the control subjects (121 +/- 48 vs. 162 +/- 75 microg/liter; P < 0.05); however, only six (26%) had values below the 10th percentile of levels seen in the control group. IGF binding protein-3 and acid labile subunit levels of the GHI adults were not significantly different from the controls. The diagnosis of GHI in an individual is extremely difficult because the patients rarely exhibit additional pituitary hormone deficits, and levels of GH-dependent proteins are normal in the majority. Diagnosis relies heavily on GH stimulation tests and requires two tests in all patients to define GHI; obesity when present is potentially a major confounder.