ACTH Synthesis Research Articles

Protein Tyrosine Phosphatase Receptors N and N2 Control Pituitary Melanotroph Development and POMC Expression.

The neuroendocrine marker genes Ptprn and Ptprn2 encode protein tyrosine phosphatase receptors N and N2, 2 members of protein tyrosine phosphatase receptors void of enzymatic activity, and whose function and mechanism of action have not been elucidated. To explore the role(s) of Ptprn and Ptprn2 on the hypothalamic-pituitary-adrenal axis, we used mice in which both genes were knocked out (DKO). The focus in this study was on corticotrophs and melanotrophs from the anterior and intermediate lobes of the pituitary gland, respectively. In both sexes, DKO caused an increase in the expression of the corticotroph/melanotroph genes Pomc and Tbx19 and the melanotroph-specific gene Pax7. We also found in vivo and in vitro increased synthesis and release of beta-endorphin, alpha-melanocyte-stimulating hormone, and ACTH in DKO mice, which was associated with increased serum corticosterone levels and adrenal mass. DKO also increased the expression of other melanotroph-specific genes, but not corticotroph-specific genes. The dopaminergic pathway in the hypothalamus and dopaminergic receptors in melanotrophs were not affected in DKO mice. However, hyperplasia of the intermediate lobe was observed in DKO females and males, accompanied by increased proopiomelanocortin immunoreactivity per cell. These results indicate that protein tyrosine phosphatase receptor type N contributes to hypothalamic-pituitary-adrenal function by being involved in processes governing postnatal melanotroph development and Pomc expression.

A Severe Case of Hypokalemic Metabolic Alkalosis: A Quiz

A Severe Case of Hypokalemic Metabolic Alkalosis: A Quiz

Silibinin, an HSP90 Inhibitor, on Human ACTH-Secreting Adenomas

Introduction: The glucocorticoid receptor is pivotal to control corticotrophin (ACTH) secretion, and its function is closely linked to the heat shock protein 90 (HSP90) chaperone complex. Impaired sensitivity to glucocorticoid feedback is a hallmark of human corticotroph adenomas, i.e., Cushing’s disease, a disorder with few medical treatment options. Silibinin, a HSP90 inhibitor, has been studied in tumoral corticotroph cells and its use proposed in Cushing’s disease. Aim of the present study was to further investigate the effect of silibinin on human corticotroph adenomas in vitro. Methods: Seven human ACTH-secreting pituitary adenomas were established in culture and treated with 10–50 µm silibinin with/without dexamethasone for up to 72 h. ACTH medium levels were measured, and POMC and glucocorticoid receptor, i.e., NR3C1, gene expression assessed. Results: Silibinin reduced spontaneous ACTH secretion and restored sensitivity to steroid negative feedback to a different extent in individual adenomas. POMC expression was decreased in both control and dexamethasone-treated wells in specimens sensitive to silibinin. Interestingly, silibinin reduced constitutive NR3C1 expression and reversed the dexamethasone-induced inhibition. Conclusions: Our findings indicate that silibinin can inhibit ACTH synthesis and secretion in individual human corticotroph adenomas and directly affects NR3C1 gene expression. These results reveal promising effects of this HSP90 inhibitor on human corticotroph adenomas and support an innovative target treatment for patients with Cushing’s disease.

Evidence for progesterone acting as an inhibitor of stress axis via stimulating pituitary neuropeptide B/W receptor 2 (NPBWR2) expression in chickens

In vertebrates, the hypothalamus-pituitary-adrenal gland (HPA) axis is the main endocrine pathway regulating the stress response, thus also called the stress axis. It has been well-accepted that the stress axis is tightly controlled by both hypothalamic stimulators and inhibitors [e.g. corticotropin (ACTH)-releasing inhibitory factor (CRIF)]. However, the identity of authentic CRIF remains unclear for decades. Recently, neuropeptide W (NPW) was proved to be the physiological CRIF in chickens. Together with its functional receptor (NPBWR2), they play critical roles in attenuating the activity of the chicken stress axis. Because increasing pieces of evidence suggested that sex steroids could regulate the stress axis, using chicken as a model, we investigated whether the newly identified CRIF and its receptor are under the control of sex steroids in this study. Our results showed that: (1) expression of NPW-NPBWR2 in the hypothalamus-pituitary axis was sexually dimorphic and developmental stage-dependent; (2) progesterone (P4), rather than 17β-estradiol (E2) and dihydrotestosterone (DHT), could dose- and time-dependently upregulate NPBWR2 expression, which was accompanied with the decrease of ACTH synthesis and secretion, in cultured pituitary cells; (3) intraperitoneal injection of P4 could elevate the mRNA level of pituitary NPBWR2; (4) P4-stimulated NPBWR2 expression was relevant to both nPR-mediated genomic action and mPRs-triggered nongenomic route associated with MEK/ERK, PI3K/AKT cascade, and calcium influx. To our knowledge, our results discover a novel route of sex steroids in modulating the stress axis of chickens, which lays a foundation to reveal the complicated interaction network between reproduction and stress axes in chickens.

Characterization of CRH-Binding Protein (CRHBP) in Chickens: Molecular Cloning, Tissue Distribution and Investigation of Its Role as a Negative Feedback Regulator within the Hypothalamus-Pituitary-Adrenal Axis.

Corticotropin (ACTH) is a pituitary hormone playing important roles in stress response within the hypothalamus–pituitary–adrenal (HPA) axis. The biosynthesis and secretion of ACTH are controlled by multiple factors, including corticotropin-releasing hormone (CRH). As a key hypothalamus-derived regulator, CRH binds to corticotropin-releasing hormone receptor 1 (CRHR1) in the anterior pituitary gland to regulate ACTH synthesis and release. Thus, CRH-binding protein (CRHBP), which binds CRH with high affinity to inhibit CRH-induced ACTH secretion from pituitary cells, draws wide attention. In contrast to the extensive investigation of CRHBP in mammals and other lower vertebrates, the gene structure, tissue expression and physiological functions of CRHBP in birds remain largely unknown. In the present study, using chicken (c-) as our animal model, we examined the gene structure, tissue expression and functionality of CRHBP. Our results showed that: (1) cCRHBP cDNA encodes a 345 amino acid precursor, which shares high sequence identity with that of mammals, reptiles, frogs and fish; (2) cCRHBP is abundantly expressed in the brain (cerebrum and hypothalamus), pituitary and ovary; (3) cCRHBP inhibits the signaling of cCRHRs induced by cCRH, thus reducing the cCRH-induced ACTH secretion from cultured chick pituitary cells; (4) stress mediators (e.g., glucocorticoids) and stress significantly upregulate CRHBP mRNA expression in chickens, supporting its role as a negative feedback regulator in the HPA axis. The present study enriches our understanding of the conserved roles of CRHBP across vertebrates. In addition, chicken is an important poultry animal with multiple economic traits which are tightly controlled by the HPA axis. The characterization of the chicken CRHBP gene helps to reveal the molecular basis of the chicken HPA axis and is thus beneficial to the poultry industry.

Molecular Derangements and the Diagnosis of ACTH-Dependent Cushing's Syndrome.

Endogenous Cushing's syndrome (CS) is associated with morbidities (diabetes, hypertension, clotting disorders) and shortens life because of infections, pulmonary thromboembolism, and cardiovascular disease. Its clinical presentation is immensely variable, and diagnosis and treatment are often delayed. Thus, there are many opportunities for basic and clinical research leading to better tests, faster diagnosis, and optimized medical treatments. This review focuses on CS caused by excessive adrenocorticotropin (ACTH) production. It describes current concepts of the regulation of ACTH synthesis and secretion by normal corticotropes and mechanisms by which dysregulation occurs in corticotrope (termed "Cushing's disease") and noncorticotrope (so-called ectopic) ACTH-producing tumors. ACTH causes adrenal gland synthesis and pulsatile release of cortisol; the excess ACTH in these forms of CS leads to the hypercortisolism of endogenous CS. Again, the differences between healthy individuals and those with CS are highlighted. The clinical presentations and their use in the interpretation of CS screening tests are described. The tests used for screening and differential diagnosis of CS are presented, along with their relationship to cortisol dynamics, pathophysiology, and negative glucocorticoid feedback regulation in the two forms of ACTH-dependent CS. Finally, several gaps in current understanding are highlighted in the hope of stimulating additional research into this challenging disorder.

Effect of silibinin on acth synthesis and secretion in human adenomatous corticotropes in vitro

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Approach to patients with bilateral adrenal incidentalomas.

The current review provides a summary on the most recent developments regarding the cause, work-up and management of bilateral adrenal incidentalomas (BAI). The recent ENS@T/ESE guidelines provide comprehensive directions on the evaluation and management of patients with adrenal incidentalomas with special focus on those with bilateral tumours. Intraadrenal ACTH synthesis that may locally stimulate cortisol secretion challenging the traditionally used term 'ACTH-independent'. Inactivating mutations of a new tumour suppressor gene, armadillo repeat containing 5 (ARMC5), are implicated in a number of patients, especially those with multiple macronodules (bilateral macronodular hyperplasia) and evidence of hypercortisolism. Loss-of-function mutations of the glucocorticoid receptor gene (NR3C1) consist a new possible genetic cause of BAIs. Regarding management an increasing number of studies provide data on the benefits and safety of unilateral rather than bilateral adrenalectomy. There is also emerging data on the beneficial use of steroidogenesis inhibitors in a dosing schedule that aims to mimic the normal cortisol rhythm with promising short-term results, but the long-term clinical benefits of this approach remain to be demonstrated. The diagnostic approach consists of imaging and hormonal evaluation. Imaging characterization should be done separately for each lesion. Hormonal evaluation includes testing for primary aldosteronism, pheochromocytoma and evaluation for autonomous cortisol secretion, using the 1-mg overnight dexamethasone suppression test. Midnight cortisol or 24-h urinary-free cortisol may aid in establishing the degree of cortisol excess. In patients with hypercortisolism ACTH levels should be measured to establish ACTH-independency. The appropriate management of BAI associated with cortisol excess remains controversial. Bilateral adrenalectomy results in lifetime steroid dependency and is better reserved only for patients with overt and severe hypercortisolism. Unilateral adrenalectomy might be considered in selected patients. Medical therapy is not an established approach yet but it may be considered when control of hypercortisolism is desired, but surgery is not an option.

SAT-308 Effect of Silibinin on ACTH Synthesis and Secretion in Human Adenomatous Corticotropes in Vitro

Silibinin, a milk thistle extract with known hepatoprotective effects, has recently been shown to act upon tumoral corticotropes and revert the Cushingoid phenotype in an allograft mouse model (Riebold et al 2015). Silbinin is known to inhibit HSP90 -a chaperone to the glucocorticoid receptor- thereby restoring sensitivity to glucocorticoid negative feedback in tumoral corticotropes. Aim of the present study was to assess the effect of silibinin on ACTH synthesis and secretion by human corticotrope adenomas in vitro. Methods: Eight human ACTH-secreting pituitary adenomas were collected during surgery and established in culture as per our protocol (Pecori Giraldi et al 2011). Specimens were treated with 10 - 50 µM silibinin for up to 72 hours. ACTH medium levels were measured by Elisa; POMC expression was assessed by RT-PCR (Cassarino et al 2017). Results. Silibinin reduced spontaneous ACTH secretion to a variable extent in individual adenomas: from 32 to 79% of baseline at 4h, and 54 - 85 % of baseline at 48 and 72h. Silibinin was also effective in reinstating or enhancing sensitivity to steroid negative feedback: ACTH decreases during 10–50 µM silibinin incubation ranged from 10 to 63% of dexamethasone-treated wells at 4 hours, 70 -80% at 48 hours and 36 to 80% at 72 hours, indicating long-lasting effect on glucocorticoid sensitivity. Silibinin induced a variable decrease in POMC expression, both as regards expression in control and dexamethasone-treated wells; some specimens exhibited a marked sensitivity to the inhibitory effect, with POMC expression decreasing to less than 50% of control. Conclusions:, this data suggests that silibinin can inhibit ACTH secretion and POMC synthesis and restore sensitivity to negative glucocorticoid feedback.

Sexual Dimorphism in Cellular and Molecular Features in Human ACTH-Secreting Pituitary Adenomas

(1) Background. Cushing’s disease presents gender disparities in prevalence and clinical course. Little is known, however, about sexual dimorphism at the level of the corticotrope adenoma itself. The aim of the present study was to evaluate molecular features of ACTH-secreting pituitary adenomas collected from female and male patients with Cushing’s disease. (2) Methods. We analyzed 153 ACTH-secreting adenomas collected from 31 men and 122 women. Adenomas were established in culture and ACTH synthesis and secretion assessed in basal conditions as well as during incubation with CRH or dexamethasone. Concurrently, microarray analysis was performed on formalin-fixed specimens and differences in the expression profiles between specimens from male and female patients identified. (3) Results. ACTH medium concentrations in adenomas obtained from male patients were significantly lower than those observed in adenomas from female patients. This could be observed for baseline as well as modulated secretion. Analysis of corticotrope transcriptomes revealed considerable similarities with few, selected differences in functional annotations. Differentially expressed genes comprised genes with known sexual dimorphism, genes involved in tumour development and genes relevant to pituitary pathophysiology. (4) Conclusions. Our study shows for the first time that human corticotrope adenomas present sexual dimorphism and underlines the need for a gender-dependent analysis of these tumours. Differentially expressed genes may represent the basis for gender-tailored target therapy.

Hyponatremia in a Patient With Cancer

Hyponatremia in a Patient With Cancer

Forms of selenium in vitamin-mineral mixes differentially affect the expression of genes responsible for prolactin, ACTH, and α-MSH synthesis and mitochondrial dysfunction in pituitaries of steers grazing endophyte-infected tall fescue.

The goal of this study was to test the hypothesis that sodium selenite (inorganic Se, ISe), SEL-PLEX (organic forms of Se, OSe), vs. a 1:1 blend (MIX) of ISe and OSe in a basal vitamin-mineral (VM) mix would differentially alter pituitary transcriptome profiles in growing beef steers grazing an endophyte-infected tall fescue (E+) pasture. Predominately Angus steers (BW = 183 ± 34 kg) were randomly selected from fall-calving cows grazing E+ pasture and consuming VM mixes that contained 35 ppm Se as ISe, OSe, or MIX forms. Steers were weaned, depleted of Se for 98 d, and subjected to summer-long common grazing of a 10.1 ha E+ pasture containing 0.51 ppm ergot alkaloids. Steers were assigned (n = 8 per treatment) to the same Se-form treatments on which they were raised. Selenium treatments were administered by daily top-dressing 85 g of VM mix onto 0.23 kg soyhulls, using in-pasture Calan gates. As previously reported, serum prolactin was greater for MIX (52%) and OSe (59%) steers vs. ISe. Pituitaries were collected at slaughter and changes in global and selected mRNA expression patterns determined by microarray and real-time reverse transcription PCR analyses, respectively. The effects of Se treatment on relative gene expression were subjected to one-way ANOVA. The form of Se affected the expression of 542 annotated genes (P < 0.005). Integrated pathway analysis found a canonical pathway network between prolactin and pro-opiomelanocortin (POMC)/ACTH/α-melanocyte-stimulating hormone (α-MSH) synthesis-related proteins and that mitochondrial dysfunction was a top-affected canonical pathway. Targeted reverse transcription-PCR analysis found that the relative abundance of mRNA encoding prolactin and POMC/ACTH/α-MSH synthesis-related proteins was affected (P < 0.05) by the form of Se, as were (P ≤ 0.05) mitochondrial dysfunction-related proteins (CYB5A, FURIN, GPX4, and PSENEN). OSe steers appeared to have a greater prolactin synthesis capacity (more PRL mRNA) vs. ISe steers through decreased dopamine type two receptor signaling (more DRD2 mRNA), whereas MIX steers had a greater prolactin synthesis capacity (more PRL mRNA) and release potential by increasing thyrotropin-releasing hormone concentrations (less TRH receptor mRNA) than ISe steers. OSe steers also had a greater ACTH and α-MSH synthesis potential (more POMC, PCSK2, CPE, and PAM mRNA) than ISe steers. We conclude that form of Se in VM mixes altered expression of genes responsible for prolactin and POMC/ACTH/α-MSH synthesis, and mitochondrial function, in pituitaries of growing beef steers subjected to summer-long grazing an E+ pasture.

40 Forms of Selenium in Vitamin-Mineral Mixes Differentially Affect the Expression of Genes Responsible for Prolactin and ACTH Synthesis in Pituitaries of Steers Grazing Endophyte-Infected Tall Fescue.

40 Forms of Selenium in Vitamin-Mineral Mixes Differentially Affect the Expression of Genes Responsible for Prolactin and ACTH Synthesis in Pituitaries of Steers Grazing Endophyte-Infected Tall Fescue.

Chicken domestication changes expression of stress-related genes in brain, pituitary and adrenals

Domesticated species have an attenuated behavioral and physiological stress response compared to their wild counterparts, but the genetic mechanisms underlying this change are not fully understood. We investigated gene expression of a panel of stress response-related genes in five tissues known for their involvement in the stress response: hippocampus, hypothalamus, pituitary, adrenal glands and liver of domesticated White Leghorn chickens and compared it with the wild ancestor of all domesticated breeds, the Red Junglefowl. Gene expression was measured both at baseline and after 45 min of restraint stress. Most of the changes in gene expression related to stress were similar to mammals, with an upregulation of genes such as FKBP5, C-FOS and EGR1 in hippocampus and hypothalamus and StAR, MC2R and TH in adrenal glands. We also found a decrease in the expression of CRHR1 in the pituitary of chickens after stress, which could be involved in negative feedback regulation of the stress response. Furthermore, we observed a downregulation of EGR1 and C-FOS in the pituitary following stress, which could be a potential link between stress and its effects on reproduction and growth in chickens.We also found changes in the expression of important genes between breeds such as GR in the hypothalamus, POMC and PC1 in the pituitary and CYP11A1 and HSD3B2 in the adrenal glands. These results suggest that the domesticated White Leghorn may have a higher capacity for negative feedback of the HPA axis, a lower capacity for synthesis of ACTH in the pituitary and a reduced synthesis rate of corticosterone in the adrenal glands compared to Red Junglefowl. All of these findings could explain the attenuated stress response in the domesticated birds.

058 Summer-Long Grazing of Endophyte-Infected Tall Fescue by Growing Beef Steers Inhibits Expression of Genes Responsible for Prolactin and ACTH Synthesis

058 Summer-Long Grazing of Endophyte-Infected Tall Fescue by Growing Beef Steers Inhibits Expression of Genes Responsible for Prolactin and ACTH Synthesis

The Role of ACTH and Corticosteroids for Sepsis and Septic Shock: An Update.

Sepsis is a common disorder associated with high morbidity and mortality. It is now defined as an abnormal host response to infection, resulting in life-threatening dysfunction of organs. There is evidence from in vitro and in vivo experiments in various animal models and in patients that endotoxin or sepsis may directly and indirectly alter the hypothalamic–pituitary–adrenal response to severe infection. These alterations may include necrosis or hemorrhage or inflammatory mediator-mediated decreased ACTH synthesis, steroidogenesis, cortisol delivery to tissues, clearance from plasma, and decreased sensitivity of tissues to cortisol. Disruption of the hypothalamic–pituitary–adrenal axis may translate in patients with sepsis into cardiovascular and other organ dysfunction, and eventually an increase in the risk of death. Exogenous administration of corticosteroids at moderate dose, i.e., <400 mg of hydrocortisone or equivalent for >96 h, may help reversing sepsis-associated shock and organ dysfunction. Corticosteroids may also shorten the duration of stay in the ICU. Except for increased blood glucose and sodium levels, treatment with corticosteroids was rather well tolerated in the context of clinical trials. The benefit of treatment on survival remains controversial. Based on available randomized controlled trials, the likelihood of survival benefit is greater in septic shock versus sepsis patients, in sepsis with acute respiratory distress syndrome or with community-acquired pneumonia versus patients without these conditions, and in patients with a blunted cortisol response to 250 μg of ACTH test versus those with normal response.

Adrenalectomy facilitates ATAT1 expression and α-tubulin acetylation in ACTH-producing corticotrophs.

Microtubules play an important role in the intracellular transport of secretory granules in endocrine cells and in mitosis and the maintenance of cell morphology and are composed of heterodimers of α- and β-tubulin. α-Tubulin N-acetyltransferase 1 (ATAT1), which acetylates the lysine residue at position 40 of α-tubulin, functions not only in stabilizing microtubule structures and forming the primary cilium assembly but also in vesicular trafficking in neurons. However, the localization of ATAT1 and the role of α-tubulin acetylation in endocrine cells in the pituitary are still poorly understood. Corticotrophs in the anterior lobe of the pituitary produce and secrete adrenocorticotropin (ACTH). Although removal of the adrenal gland, a target organ of ACTH, is reported to promote the synthesis and secretion of ACTH in corticotrophs and to induce structural alterations in their organelles, uncertainty remains as to whether the acetylation of α-tubulin is involved in such intracellular events of corticotrophs. We investigate the expression and localization of ATAT1 and the acetylation of α-tubulin in the pituitary of normal and adrenalectomized rats. We find that ATAT1 is localized to the Golgi apparatus of endocrine cells in the anterior lobe of normal pituitary and that the expression levels of ATAT1 and acetylation levels of α-tubulin increase following adrenalectomy. These results agree with the hypothesis that the acetylation of α-tubulin by ATAT1 regulates the intracellular transport of secretory granules in corticotrophs.

Preincubation of Pituitary Tumor Cells With the Epidrugs Zebularine and Trichostatin A Are Permissive for Retinoic Acid-Augmented Expression of the BMP-4 and D2R Genes

Retinoic acid (RA)-induced expression of bone morphogenetic protein-4 (BMP-4) inhibits in vitro and in vivo cell proliferation and ACTH synthesis in corticotroph-derived tumor cells. Reduced expression of BMP-4 in this adenoma subtype is associated with epigenomic silencing, and similar silencing mechanisms are also associated with the RA-responsive dopamine D2 receptor (D2R) in somatolactotroph cells. We now show that preincubation with the epidrugs zebularine and trichostatin A is obligate and permissive for RA-induced expression of the BMP-4 and the D2R genes in pituitary tumor cells. Combined epidrug challenges are associated with marginal reduction in CpG island methylation. However, significant change to histone tail modifications toward those associated with expression-competent genes is apparent, whereas RA challenge alone or in combined incubations does not have an impact on these modifications. Epidrug-mediated and RA-augmented expression of endogenous BMP-4 increased or decreased cell proliferation and colony-forming efficiency in GH3 and AtT-20 pituitary tumor cells, respectively, recapitulating recent reports of challenges of these cells with exogenous ligand. The specificity of the BMP-4-mediated effects was further supported by knock-down experiments of the BMP-4 antagonist noggin (small interfering RNA [siRNA]). Knock-down of noggin, in the absence and the presence of epidrugs, induced and augmented BMP-4 expression, respectively. In cell proliferation assays, challenge with either epidrugs or siRNA led to significant increase in cell numbers at the 72-hour time point; however, in siRNA-treated cells coincubated with epidrugs, a significant increase was apparent at the 48-hour time point. These studies show the potential of combined drug challenges as a treatment option, where epidrug renders silenced genes responsive to conventional therapeutic options.

Glucocorticoid–catecholamine interplay within the composite thymopoietic regulatory network

This paper highlights the multiple putative thymic and extrathymic points of intersection and interaction between glucocorticoids (GCs) and catecholamines (CAs)--the end-point mediators of the major routes of communication between the brain and the immune system--in the context of intricate thymic T cell-developmental tuning. More specifically, we discuss in detail findings indicating that adrenal GCs can influence thymopoiesis by adjusting directly and/or indirectly (through modulation of pituitary and local ACTH synthesis) not only thymic GC synthesis, in a cell type-specific manner, but also thymic CA bioavailability (via altering CA outflow from sympathetic nerve endings and local CA synthesis), β and α(1) -adrenoceptor (AR) expression, and/or AR-mediated intracellular signal transduction in thymic cells. In addition, this short review points to GC- and CA-sensitive stages along the multistep T cell-developmental journey and the possible effects of altered GC, and consequently CA signaling, on thymopoietic efficiency.

Reversible impairment of the processing of proopiomelanocortin into ACTH in pituitary enlargement suspected of lymphocytic hypophysitis

We describe a 64-year-old woman with a cystic pituitary mass presenting with central diabetes insipidus. Brain magnetic resonance imaging (MRI) with enhancement showed enlargement of the pituitary gland with cystic portions and thickening of the pituitary stalk with homogeneous enhancement. Combined anterior pituitary stimulation test and insulin-induced hypoglycemic test confirmed the diagnosis of panhypopituitarism, including adrenocortical insufficiency due to pituitary and hypothalamic dysfunction by stalk compression. Interestingly, the response of serum cortisol to CRH was low and delayed, in contrast to the marked increase in plasma ACTH. Molecular analysis of her plasma ACTH by Sephadex G75 gel exclusion chromatography coupled with radioimmunoassay (RIA) indicated a peak for high molecular weight ACTH, i.e., proACTH, in addition to that for 1-39 ACTH. Three years later, enlargement of the pituitary gland with cystic portions and thickening of the pituitary stalk disappeared completely, followed by the decrease in plasma proACTH level. By the results of endocrinological study and the change of pituitary MRI findings, lymphocytic hypophysitis was suggested. Synthesis of immature ACTH is generally thought to be due to impaired processing of the precursor proopiomelanocortin (POMC) through activation of prohormone convertase (PC)-1 by CRH. It is possible that the immature ACTH in this case was produced by impaired processing of the precursor POMC due to decreased CRH, dysfunction of corticotrophs in the anterior pituitary by compression of the normal pituitary, or antibodies targeting hypothalamic and/or pituitary cells. This report suggested that impaired processing of POMC may unusually play a role in adrenocortical insufficiency exhibited in lymphocytic hypophysitis.