Determination of glucose cut-off points for optimal performance of glucagon stimulation test.

Introduction: The glucagon stimulation test (GST) is widely used to assess growth hormone (GH) and cortisol secretion, nevertheless the precise mechanisms underpinning these hormonal responses remain unclear. We have endeavoured to explore the relationship between glucose and insulin fluctuations during GST and their impact on GH and cortisol secretion. Subjects and methods: We retrospectively studied 139 subjects (mean age 35.5 ± 15.1 years, BMI 26.6 ± 6.61 kg/m²), including 62 individuals with a history of pituitary disease (27 with an intact adrenal axis) and 77 healthy controls. Standard dose intramuscular GST was performed in all subjects. Results: Once BMI and age were excluded from multivariate model, the nadir of glucose concentration during GST was the sole variable associated with maximal GH secretion (ΔGH, p<0.0003), while neither glucose/insulin peak, nor Δglucose/Δinsulin concentrations contributed to ΔGH. 100% pass rate for GH secretion above 3 ng/ml or 1.07 ng/ml cut-offs was observed for glucose concentrations at, or below 60 mg/dl (3.33 mmol/l) (for Controls), or 62 mg/dl (3.44 mmol/l) (for Controls and patients with an intact adrenocortical axis). Such low glucose concentrations were obtained, however, only in about 30% of studied individuals. Conversely, cortisol secretion did not correlate with glucose or insulin fluctuations, suggesting alternative regulatory mechanisms. Conclusions: This study reveals that glucose nadir below 3.33 mmol/l is the only biochemical biovariable linked with optimal GH secretion during GST, whereas mechanisms responsible for cortisol secretion remain unclear. We emphasize the importance of glucose monitoring during GST to validate GH stimulation and support clinical decisions in GH deficiency management.

Postnatal Development and Maintenance of Functional Pituitary Gonadotrophs Is Dependent on PI4-Kinase A.

Postnatal development of functional pituitary gonadotrophs is necessary for maturation of the hypothalamic-pituitary-gonadal axis, puberty, and reproduction. Here we examined the role of PI4-kinase A, which catalyzes the biosynthesis of PI4P in mouse reproduction by knocking out this enzyme in cells expressing the gonadotropin-releasing hormone (GnRH) receptor. Knockout (KO) mice were infertile, reflecting underdeveloped gonads and reproductive tracts and lack of puberty. The number and distribution of hypothalamic GnRH neurons and Gnrh1 expression in postnatal KOs were not affected, whereas Kiss1/kisspeptin expression was increased. KO of PI4-kinase A also did not alter embryonic establishment and neonatal development and function of the gonadotroph population. However, during the postnatal period, there was a progressive loss of expression of gonadotroph-specific genes, including Fshb, Lhb, and Gnrhr, accompanied by low gonadotropin synthesis. The postnatal gonadotroph population also progressively declined, reaching approximately one-third of that observed in controls at 3 months of age. In these residual gonadotrophs, GnRH-dependent calcium signaling and calcium-dependent membrane potential changes were lost, but intracellular administration of inositol-14,5-trisphosphate rescued this signaling. These results indicate a key role for PI4-kinase A in the postnatal development and maintenance of a functional gonadotroph population.

The hidden hedgehog of the pituitary: hedgehog signaling in development, adulthood and disease of the hypothalamic-pituitary axis.

Hedgehog signaling plays pivotal roles in embryonic development, adult homeostasis and tumorigenesis. However, its engagement in the pituitary gland has been long underestimated although Hedgehog signaling and pituitary embryogenic development are closely linked. Thus, deregulation of this signaling pathway during pituitary development results in malformation of the gland. Research of the last years further implicates a regulatory role of Hedgehog signaling in the function of the adult pituitary, because its activity is also interlinked with homeostasis, hormone production, and most likely also formation of neoplasms of the gland. The fact that this pathway can be efficiently targeted by validated therapeutic strategies makes it a promising candidate for treating pituitary diseases. We here summarize the current knowledge about the importance of Hedgehog signaling during pituitary development and review recent data that highlight the impact of Hedgehog signaling in the healthy and the diseased adult pituitary gland.

The Hypothalamus-pituitary-adrenocortical Response to Critical Illness: A Concept in Need of Revision.

Based on insights obtained during the past decade, the classical concept of an activated hypothalamus-pituitary-adrenocortical axis in response to critical illness is in need of revision. After a brief central hypothalamus-pituitary-adrenocortical axis activation, the vital maintenance of increased systemic cortisol availability and action in response to critical illness is predominantly driven by peripheral adaptations rather than by an ongoing centrally activated several-fold increased production and secretion of cortisol. Besides the known reduction of cortisol-binding proteins that increases free cortisol, these peripheral responses comprise suppressed cortisol metabolism in liver and kidney, prolonging cortisol half-life, and local alterations in expression of 11ßHSD1, glucocorticoid receptor-α (GRα), and FK506 binding protein 5 (FKBP51) that appear to titrate increased GRα action in vital organs and tissues while reducing GRα action in neutrophils, possibly preventing immune-suppressive off-target effects of increased systemic cortisol availability. Peripherally increased cortisol exerts negative feed-back inhibition at the pituitary level impairing processing of pro-opiomelanocortin into ACTH, thereby reducing ACTH-driven cortisol secretion, whereas ongoing central activation results in increased circulating pro-opiomelanocortin. These alterations seem adaptive and beneficial for the host in the short term. However, as a consequence, patients with prolonged critical illness who require intensive care for weeks or longer may develop a form of central adrenal insufficiency. The new findings supersede earlier concepts such as "relative," as opposed to "absolute," adrenal insufficiency and generalized systemic glucocorticoid resistance in the critically ill. The findings also question the scientific basis for broad implementation of stress dose hydrocortisone treatment of patients suffering from acute septic shock solely based on assumption of cortisol insufficiency.

Novel Candidate Regulators and Developmental Trajectory of Pituitary Thyrotropes.

The pituitary gland regulates growth, metabolism, reproduction, the stress response, uterine contractions, lactation, and water retention. It secretes hormones in response to hypothalamic input, end organ feedback, and diurnal cues. The mechanisms by which pituitary stem cells are recruited to proliferate, maintain quiescence, or differentiate into specific cell types, especially thyrotropes, are not well understood. We used single-cell RNA sequencing in juvenile P7 mouse pituitary cells to identify novel factors in pituitary cell populations, with a focus on thyrotropes and rare subtypes. We first observed cells coexpressing markers of both thyrotropes and gonadotropes, such as Pou1f1 and Nr5a1. This was validated in vivo by both immunohistochemistry and lineage tracing of thyrotropes derived from Nr5a1-Cre; mTmG mice and demonstrates that Nr5a1-progenitors give rise to a proportion of thyrotropes during development. Our data set also identifies novel factors expressed in pars distalis and pars tuberalis thyrotropes, including the Shox2b isoform in all thyrotropes and Sox14 specifically in Pou1f1-negative pars tuberalis thyrotropes. We have therefore used single-cell transcriptomics to determine a novel developmental trajectory for thyrotropes and potential novel regulators of thyrotrope populations.

Subcutaneous transplantation of human embryonic stem cells-derived pituitary organoids.

Introduction: The pituitary gland, regulating various hormones, is central in the endocrine system. As spontaneous recovery from hypopituitarism is rare, and exogenous-hormone substitution is clumsy, pituitary replacement via regenerative medicine, using pluripotent stem cells, is desirable. We have developed a differentiation method that in mice yields pituitary organoids (POs) derived from human embryonic stem cells (hESC). Efficacy of these POs, transplanted subcutaneously into hypopituitary mice, in reversing hypopituitarism was studied. Methods: hESC-derived POs were transplanted into inguinal subcutaneous white adipose tissue (ISWAT) and beneath dorsal skin, a relatively avascular region (AR), of hypophysectomized severe combined immunodeficient (SCID) mice. Pituitary function was evaluated thereafter for ¾ 6mo, assaying basal plasma ACTH and ACTH response to corticotropin-releasing hormone (CRH) stimulation. Histopathologic examination of organoids 150d after transplantation assessed engraftment. Some mice received an inhibitor of vascular endothelial growth factor (VEGF) to permit assessment of how angiogenesis contributed to subcutaneous engraftment. Results: During follow-up, both basal and CRH-stimulated plasma ACTH levels were significantly higher in the ISWAT group (p < 0.001 - 0.05 and 0.001 - 0.005, respectively) than in a sham-operated group. ACTH secretion also was higher in the ISWAT group than in the AR group. Histopathologic study found ACTH-producing human pituitary-cell clusters in both groups of allografts, which had acquired a microvasculature. POs qPCR showed expression of angiogenetic factors. Plasma ACTH levels decreased with VEGF-inhibitor administration. Conclusions: Subcutaneous transplantation of hESC-derived POs into hypopituitary SCID mice efficaciously renders recipients ACTH-sufficient.

Correlation of pituitary histomorphometry with dopamine and dopamine D2 receptor expression in horses with pituitary pars intermedia dysfunction.

Pituitary pars intermedia dysfunction (PPID) is an endocrinopathy commonly affecting old horses. It is a spontaneously occurring, progressive disease that is still poorly understood. Previous studies have observed neurodegeneration of the dopaminergic inhibition of melanotrophs, which leads to decreased dopamine (DA) in the pars intermedia (PI) and increased pro-opiomelanocortin-derived peptides circulating in plasma. However, rats knockout for the dopamine D2 receptor (D2r) similarly develop PI hypertrophy and hyperplasia. Thus, based on the current pathophysiological theory of PPID, whether the decreased DA or the D2r dysfunction leads to PPID is still unclear. To test this, a total of 28 retrospective cases of horses with PPID were collected, graded and the expression of tyrosine hydroxylase (TH) and D2r in the PI were determined. The histological and immunohistochemical results demonstrated that horses with higher tumor histological grades had reduced TH expression with increased D2r immunoreactivity colocalized in the PI (p < 0.001, p < 0.05 respectively). This correlation supports the role of DA in the pathogenesis of continuous unregulated proliferation of neoplastic cells in PI and indicates the efficiency of D2r agonists as a treatment for PPID.

Activation of Age-Related Nuclear Factor-κB Signaling Pathway Leads to Chronic Inflammation and Pituitary Fibrosis.

OBJECTIVE: The purpose of the present study was to investigate the mechanism of pituitary fibrosis in elderly people. METHODS: First, 20 pituitary glands obtained from 11 elderly people and 9 young people were studied using Masson's trichrome staining for fibrosis detection. Second, pituitary glands from 12 male rats, including 6 aged rats (OM group) and 6 young rats (YM group), were also studied. Western blotting was performed to detect collagen 1 and phosphorylation of the nuclear factor (NF)-κB subunit p65 in the OM and YM groups. The levels of 8 proinflammatory cytokines (interleukin [IL]-1α, IL-1ß, IL-2, IL-4, IL-6, IL-8, interferon-γ, and tumor necrosis factor-α) in the rat pituitary glands were detected using liquid suspension chip technology. Enzyme-linked immunosorbent assays were performed to detect the growth hormone (GH) levels in the venous blood samples from the rats. Next, 12 aged rats were randomly divided into 2 groups: the QNZ (Q)+OM and normal physiological saline (N)+OM groups. The Q+OM and N+OM groups had undergone intervention by intraperitoneally injection of QNZ and physiological saline (1 mg/kg) for 28 days, respectively. Finally, biochemical and histological examinations were performed, including Masson's trichrome staining for fibrosis, Western blotting for phosphorylation of p65, Millipore multiplex bead arrays (Millipore, Billerica, Massachusetts, USA) for proinflammatory cytokine levels, and enzyme-linked immunosorbent assays for GH secretion. RESULTS: Fibrosis was detected in the elderly patient group. Collagen 1, phosphorylation of the NF-κB signaling pathway, and the proinflammatory cytokine levels showed a significant increase in the OM group. Compared with the N+OM group, pituitary fibrosis was alleviated in the Q+OM group, with an increase in GH secretion and decreased proinflammatory cytokine levels and NF-κB. CONCLUSIONS: Pituitary fibrosis was found in the elderly group, and the pathological change was antagonized by decreasing the proinflammatory cytokine levels using QNZ and further increasing GH secretion.

Evaluation of sex hormone profile and semen parameters in acromegalic male patients.

OBJECTIVE: To investigate the changes in semen quality and bioavailable testosterone concentrations in acromegalic male patients according to their disease activity and compare them with patients with non-functional pituitary adenoma (NFA) and healthy controls (HC). METHODS: Twenty-four acromegalic patients with active disease, 22 acromegalic patients in remission, 10 HCs, and 10 patients with NFA were included. RESULTS: Total and calculated bioavailable testosterone concentrations were lower in patients with pituitary disease. Patients with acromegaly had more severely impaired total testosterone levels and semen parameters in comparison to HCs and patients with NFA. The degree of impairment was more prominent in acromegalic patients with active disease than acromegalic patients in remission. Acromegalic patients in remission had residual impairments in both semen quality and testosterone concentrations. Patients with NFA had the lowest concentrations of calculated bioavailable testosterone, followed by acromegalic patients with active disease and acromegalic patients in remission. Increasing growth hormone (GH) levels were found to be associated with both more severely impaired semen quality and androgen concentrations. CONCLUSION: Growth hormone hypersecretion can disturb reproductive biology and thereof semen quality. The reduction in semen quality and androgen levels may not fully recover upon disease control. Clinicians should be aware of the increased risk of impaired semen parameters and reduced total/bioavailable levels in acromegalic patients, especially in the setting of active disease.

Lipotoxicity suppresses the synthesis of growth hormone in pituitary somatotrophs via endoplasmic reticulum stress.

Lipotoxicity has been shown to cause dysfunction of many organs and tissues. However, it is unclear whether lipotoxicity is harmful to the somatotrophs, a kind of cell that synthesize growth hormone (GH) in the pituitary. In this study, we performed an epidemiological study, serum levels of triglyceride (TG) and GH showed a negative correlation, even after adjustment for potential confounders. In an animal study, male Sprague-Dawley rats were fed a high-fat diet (HFD) or a control diet for 28 weeks. HFD rats showed impaired GH synthesis, resulting in a decrease in circulating GH levels. The expression of pituitary Pit-1, a key transcription factor of GH, was inhibited. We found that the inositol-requiring enzyme 1α (IRE1α) pathway of endoplasmic reticulum (ER) stress was triggered in HFD rat pituitary glands and palmitic acid-treated GH3 cells, respectively. On the contrary, applying 4-phenyl butyric acid (4-PBA) to alleviate ER stress or 4µ8c to specifically block the IRE1α pathway attenuated the impairment of both Pit-1 and GH expression. In conclusion, we demonstrated that lipotoxicity directly inhibits the synthesis of GH, probably by reducing Pit-1 expression. The IRE1α signaling pathway of ER stress may play an important role in this process.

Lung aspergilloma with pituitary invasive aspergillosis presenting as headache and hyponatraemia.

Fungal infections involving the pituitary gland are rare and can be life threatening. A 75-year-old man with hypertension and diabetes mellitus presented with headache and hyponatraemia. Imaging study showed right upper lung mass, and mass resection showed aspergilloma without tissue invasion on histology. The patient developed visual impairment a few weeks later, and MRI of the brain revealed bilateral sphenoid sinusitis and pituitary invasion. The trans-sphenoidal biopsy confirmed invasive Aspergillus infection. His sphenoidal sinuses were endoscopically debrided, and he was treated with oral voriconazole. Pituitary aspergillosis should be considered in the differential diagnosis in patients with lung aspergilloma with headache and sinusitis. Prompt biopsy and antifungal treatment are important due to the high mortality rate of the infection.

The evaluation of pituitary damage associated with cardiac arrest: An experimental rodent model.

The pituitary gland plays an important endocrinal role, however its damage after cardiac arrest (CA) has not been well elucidated. The aim of this study was to determine a pituitary gland damage induced by CA. Rats were subjected to 10-min asphyxia and cardiopulmonary resuscitation (CPR). Immunohistochemistry and ELISA assays were used to evaluate the pituitary damage and endocrine function. Samples were collected at pre-CA, and 30 and 120 min after cardio pulmonary resuscitation. Triphenyltetrazolium chloride (TTC) staining demonstrated the expansion of the pituitary damage over time. There was phenotypic validity between the pars distalis and nervosa. Both CT-proAVP (pars nervosa hormone) and GH/IGF-1 (pars distalis hormone) decreased over time, and a different expression pattern corresponding to the damaged areas was noted (CT-proAVP, 30.2 ± 6.2, 31.5 ± 5.9, and 16.3 ± 7.6 pg/mg protein, p < 0.01; GH/IGF-1, 2.63 ± 0.61, 0.62 ± 0.36, and 2.01 ± 0.41 ng/mg protein, p < 0.01 respectively). Similarly, the expression pattern between these hormones in the end-organ systems showed phenotypic validity. Plasma CT-proAVP (r = 0.771, p = 0.025) and IGF-1 (r = -0.775, p = 0.024) demonstrated a strong correlation with TTC staining area. Our data suggested that CA induces pathological and functional damage to the pituitary gland.

The Effect of Pituitary Gland Disorders on Glucose Metabolism: From Pathophysiology to Management.

This review aims to explore, present, and discuss disorders of glucose metabolism implicated in pituitary gland diseases, the appropriate interventions, as well as the therapeutic challenges that may arise. Pituitary pathologies may dysregulate glucose homeostasis, as both the excess and deficiency of various pituitary hormones can affect glucose metabolism. Increased circulating levels of growth hormone, glucocorticoids or prolactin have been shown to mainly provoke hyperglycemic states, while hypopituitarism can be associated with both hyperglycemia and hypoglycemia. Addressing the primary cause of these disorders with the use of surgery, medical treatment or radiotherapy forms the cornerstone of current management strategies. Physicians should bear in mind that some such medications have an unfavorable effect on glucose metabolism too. When unsuccessful, or until the appropriate treatment of the underlying pituitary problem, the addition of established antidiabetic therapies might prove useful. Further studies aiming to discover more accurate and effective drug preparations in combination with optimal lifestyle management models will contribute to achieving a more successful glycemic control in these patients.

Genetic Anomalies of Growth Hormone Deficiency in Pediatrics.

Several different proteins regulate, directly or indirectly, the production of growth hormones from the pituitary gland, thereby complex genetics is involved. Defects in these genes are related to the deficiency of growth hormones solely, or deficiency of other hormones, secreted from the pituitary gland including growth hormones. These studies can aid clinicians to trace the pattern of the disease between the families, start early treatment and predict possible future consequences. This paper highlights some of the most common and novel genetic anomalies concerning growth hormones, which are responsible for various genetic defects in isolated growth and combined pituitary hormone deficiency disease.

Human pituitary development and application of iPSCs for pituitary disease.

The pituitary plays a pivotal role in maintaining systemic homeostasis by secreting several hormones. During fetal development, the pituitary develops from the oral ectoderm in contact with the adjacent hypothalamus. This process is regulated by the fine-tuned expression of transcription and growth factors. Impairments of this process result in congenital pituitary hypoplasia leading to dysfunction of the pituitary. Although animal models such as knockout mice have helped to clarify these underlying mechanisms, the developmental processes of the human pituitary gland and the mechanisms of human pituitary disorders have not been fully understood. This is because, at least in part, of the lack of a human pituitary developmental model. Recently, methods for in vitro induction of the pituitary gland from human pluripotent stem cells were developed. These models can be utilized not only for regenerative medicine but also for human pituitary studies on developmental biology and for modeling of pituitary disorders, such as hypopituitarism and pituitary tumors. In this review, we provide an overview of recent progress in the applications of pluripotent stem cells for pituitary research and discuss further perspectives for pituitary studies.

Proteína moduladora de la actividad del receptor de aril hidrocarburos (AIP): genética, bioquímica e impacto clínico / Aryl hydrocarbon receptor interacting protein (AIP): genetics, biochemistry and clinical impact

El gen AIP (proteína moduladora de la actividad del receptor de aril hidrocarburos) se localiza en la región 11q13.2 y codifica para una proteína de 330 aminoácidos que interactúa con el factor de transcripción AhR (receptor para aril hidrocarburos). Las mutaciones en este gen se han asociado con adenomas pituitarios aislados de tipo familiar (APAF). Se caracterizan por una presentación temprana (alrededor de 20 años), por lo regular producen hormona de crecimiento y/o prolactina, tienen un comportamiento clínico agresivo y poca respuesta a análogos de somatostatina.

The AIP gene (aryl hydrocarbon receptor interacting protein) is located on chromosome 11q13.2 and encodes a 330 amino acid protein which interacts with the aryl hydrocarbon receptor (AHR) transcription factor. Mutations in the AIP gene have been associated with familial isolated pituitary adenomas (FIPA). They characterize by an early-onset (around the age of 20 years old) and for being aggressive, growth hormone and/or prolactin-secreting tumors, with poor response to somatostatin analogues.

Cushing's Syndrome in a Patient With Rathke's Cleft Cyst and ACTH Cell Hyperplasia Detected by 11C-Methionine PET Imaging-A Case Presentation.

Background: Adrenocorticotropic Hormone (ACTH)-dependent Cushing's Syndrome (CS) is most often caused by a pituitary adenoma. Although rarely, it can also result from pituitary corticotroph cell hyperplasia (CH). Reports on concomitant pituitary lesions including ACTH-producing adenomas and Rathke's cleft cysts (RCCs) have been published. Positron emission tomography (PET), using 11C-labelled-methionine (MET) as a tracer and co-registered with magnetic resonance imaging (MRI) has been shown to be useful in the diagnosis of pituitary collision lesions, however, its role is still under investigation. In this work we present the case of a patient in whom CS was caused by non-adenomatous CH within the wall of an RCC. Case Summary: In 2015 a patient with signs and symptoms of CS was referred to our Department. Biochemical studies repeatedly showed elevated midnight serum cortisol and ACTH levels. Magnetic resonance imaging of the sellar region revealed an RCC and MET-PET/MR showed heterogeneous labelled-methionine metabolism in the vicinity of the cyst's wall. Transsphenoidal surgery resulted in rapid, complete and lasting relief of symptoms. Histopathological examination demonstrated an RCC and CH. Conclusions: Concomitance of pituitary focal lesions is a rare phenomenon. Methionine-labelled PET/MR may be useful in the diagnosis of collision sellar lesions, including CH. Corticotroph cell hyperplasia can present as mild and fluctuating hypercortisolaemia.

Effects of advanced age and pituitary pars intermedia dysfunction on components of the acute phase reaction in horses.

Age, neurodegenerative disorders, and dysfunction of insulin secretion may be correlated with increased systemic concentrations of acute phase markers. Thus, the study aimed to determine the effect of age, pituitary pars intermedia dysfunction (PPID), and insulin dysregulation (ID) associated with PPID, on markers of the acute phase reaction. Twenty-nine mix-breed horses of both sexes were classified into groups: (1) healthy adult controls, (2) healthy non-PPID geriatric horses, (3) PPID ID+ horses, and (4) PPID ID- horses. Whole blood proinflammatory cytokine gene expression and serum concentrations of pro- and anti-inflammatory cytokines and acute phase proteins were measured. The data were analyzed using the Mann-Whitney U-test, and correlations between groups of data were assessed using Spearman's correlation coefficient. The tests were statistically significant if P < 0.05. No differences in the whole blood cytokine gene expression, serum cytokine concentrations, or acute phase proteins were noted between the groups. In the PPID ID group, there was a strong correlation between the ACTH concentration after the administration of thyrotropin-releasing hormone and the expression of IL-8 (r = 0.941; P = 0.0321). In the PPID ID+ group, there was a strong correlation between basal insulin concentrations and serum amyloid A (SAA; r = 0.936; P = 0.0083) as well as between postprandial insulin concentrations and SAA (r = 0.965; P = 0.001). These data suggest that neurodegeneration in horses moderately affects circulating markers of inflammation and that ID in horses with PPID influences acute phase inflammatory markers.

Development of the Pituitary Gland.

The development of the anterior pituitary gland occurs in distinct sequential developmental steps, leading to the formation of a complex organ containing five different cell types secreting six different hormones. During this process, the temporal and spatial expression of a cascade of signaling molecules and transcription factors plays a crucial role in organ commitment, cell proliferation, patterning, and terminal differentiation. The morphogenesis of the gland and the emergence of distinct cell types from a common primordium are governed by complex regulatory networks involving transcription factors and signaling molecules that may be either intrinsic to the developing pituitary or extrinsic, originating from the ventral diencephalon, the oral ectoderm, and the surrounding mesenchyme. Endocrine cells of the pituitary gland are organized into structural and functional networks that contribute to the coordinated response of endocrine cells to stimuli; these cellular networks are formed during embryonic development and are maintained or may be modified in adulthood, contributing to the plasticity of the gland. Abnormalities in any of the steps of pituitary development may lead to congenital hypopituitarism that includes a spectrum of disorders from isolated to combined hormone deficiencies including syndromic disorders such as septo-optic dysplasia. Over the past decade, the acceleration of next-generation sequencing has allowed for rapid analysis of the patient genome to identify novel mutations and novel candidate genes associated with hypothalmo-pituitary development. Subsequent functional analysis using patient fibroblast cells, and the generation of stem cells derived from patient cells, is fast replacing the need for animal models while providing a more physiologically relevant characterization of novel mutations. Furthermore, CRISPR-Cas9 as the method for gene editing is replacing previous laborious and time-consuming gene editing methods that were commonly used, thus yielding knockout cell lines in a fraction of the time. © 2020 American Physiological Society. Compr Physiol 10:389-413, 2020.

Pituitary Hyperplasia, Hormonal Changes and Prolactinoma Development in Males Exposed to Estrogens-An Insight From Translational Studies.

Estrogen signaling plays an important role in pituitary development and function. In sensitive rat or mice strains of both sexes, estrogen treatments promote lactotropic cell proliferation and induce the formation of pituitary adenomas (dominantly prolactin or growth-hormone-secreting ones). In male patients receiving estrogen, treatment does not necessarily result in pituitary hyperplasia, hyperprolactinemia or adenoma development. In this review, we comprehensively analyze the mechanisms of estrogen action upon their application in male animal models comparing it with available data in human subjects. Sex-specific molecular targets of estrogen action in lactotropic (PRL) cells are highlighted in the context of their proliferative and secretory activity. In addition, putative effects of estradiol on the cellular/tumor microenvironment and the contribution of postnatal pituitary progenitor/stem cells and transdifferentiation processes to prolactinoma development have been analyzed. Finally, estrogen-induced morphological and hormone-secreting changes in pituitary thyrotropic (TSH) and adrenocorticotropic (ACTH) cells are discussed, as well as the putative role of the thyroid and/or glucocorticoid hormones in prolactinoma development, based on the current scarce literature.