The pituitary gland: embryology, physiology, and pathophysiology

Characterization of hair cortisol concentration pre-conception and during pregnancy

BACKGROUND

The hypothalamic pituitary adrenal (HPA) axis is a system involved in stress and pregnancy regulation, and hair cortisol concentration (HCC) is a promising biomarker of its activity. Assessing factors that influence HCC in the prenatal period is critical to understand whether and how HPA axis (dys-)regulation influences maternal health and child development, particularly in high-risk populations from low- and middle-income countries (LMICs).

AIMS

This study aimed at characterizing preconception and pregnancy HCC with respect to multiple sociodemographic, pregnancy-related, and hair-related factors.

METHODS

In a sample of N = 2581 pregnant women in Perú, participants from two cohort studies provided a 6 cm scalp hair sample at three prenatal timepoints. Each hair sample was cut into two segments of 3 cm that represent cortisol secretion at four times: preconception, first-, second- and third trimester of pregnancy. Hair cortisol was extracted using liquid chromatography tandem mass spectrometry (LC-MS/MS). Spearman correlations, paired t-tests, and ANOVA were used to assess differences in log-transformed values of HCC (logHCC) across maternal sociodemographic, pregnancy-related, and hair-related factors. Multivariable linear regressions were used to examine independent associations of HCCs with selected correlates.

RESULTS

Mean logHCC values showed an increase across the four prenatal periods. Preconception BMI was consistently associated with HCC in all three trimesters, while difficulty accessing basic foods, education, hair dyeing, and infant sex showed time-specific associations with HCCs. In sensitivity analyses, we detected no substantial segment effects in the associations of HCCs with maternal characteristics.

CONCLUSION

This study is the largest to characterize HCC in pregnant women from a LMIC. Our findings provide a foundation for the use of HCC as a biomarker of prenatal HPA axis activity for future studies. This foundation may contribute to finding valid biomarkers of stress-response systems to promote maternal and child health.

The association between maternal prenatal hair cortisol concentration and preterm birth: A systematic review and meta-analysis

BACKGROUND

The risk of preterm birth (PTB) increases when experiencing stress during pregnancy. Chronic stress has been associated with a dysregulation of the hypothalamic-pituitary-adrenal axis, for which hair cortisol concentration (HCC) is a promising biomarker. However, previous studies on the association between HCC and PTB yielded inconsistent results. This systematic review and meta-analysis synthesized previous studies on the association between maternal HCC before and during pregnancy and spontaneous PTB.

METHODS

Data was extracted from N = 11 studies with k = 19 effect sizes retrieved from PubMed, Embase, Web of Science, CINAHL and citation searching by hand in June 2023 and updated in October 2023. Standardized mean differences were calculated, and a random-effects three-level meta-analysis was conducted. Effect heterogeneity was assessed using Q and I2.

RESULTS

HCC during pregnancy was higher among PTB than term groups, but effects were not statistically significant (z = 0.11, 95% CI: - 0.28, 0.51, p = .54) and total heterogeneity was high (Q16 = 60.01, p < .001, I2Total = 92.30%). After leaving out two possible outlier studies in sensitivity analyses, HCC was lower among preterm compared to term delivering groups, although not statistically significant (z = - 0.06, 95% CI: - 0.20, 0.08, p = .39) but with a substantially reduced total heterogeneity (Q12 = 16.45, p = .17, I2Total = 42.15%). No moderators affected the estimates significantly, but an effect of trimester and gestational age at delivery is likely.

CONCLUSION

There is currently no evidence of prenatal HCC differences between PTB and term groups as effects were small, imprecise, and not significant. Low statistical power and methodological weaknesses of the small-scale studies challenge possible biological inferences from the small effects, but further research on HCC during pregnancy is highly encouraged.

The Association Between Pre-Pregnancy and First-Trimester Hair Cortisol and Preterm Birth: A Causal Inference Model

Background Adverse life events and chronic psychological distress before and during pregnancy have frequently been associated with preterm birth (PTB) but the biological underpinnings remain unclear. We investigated the association between corticosteroid levels in pre-pregnancy and first-trimester hair and the risk of PTB. Methods We followed 1,808 pregnant women from a prospective pre-birth cohort study in Lima, Perú. Hair samples were taken at the end of the first pregnancy trimester. The two most proximal 3cm segments to the scalp (representing pre-pregnancy and first-trimester) were analyzed to obtain hair cortisol and cortisone concentrations (HCC and HCNC). PTB was defined as birth < 37 completed gestational weeks. We constructed four generalized propensity scores for pre-pregnancy and first-trimester HCC and HCNC to create corresponding inverse probability weights before fitting marginal structural models for estimating the effect of HCC and HCNC on PTB risk. Results Pre-pregnancy Log HCC was not independently associated with PTB risk (RR = 0.97; 95%CI: 0.79, 1.19). In contrast, one SD increase from the mean first-trimester Log HCC was independently associated with a 37% (95%CI: 1.11, 1.69) increased risk of PTB. Although imprecise, pre-pregnancy Log HCNC was negatively associated with PTB risk (RR = 0.84; 95%CI: 0.58, 1.20), whereas the association between first-trimester Log HCNC and PTB risk was positive (RR = 1.20; 95%CI: 0.87, 1.65). Conclusions Our findings show that chronic corticosteroid levels in early pregnancy are causally linked to PTB risk in pregnant Peruvian women. This finding contributes to understanding the biological underpinnings of PTB better to enhance PTB prevention.

Intrasellar Dermoid Cyst: Case Report of a Rare Lesion and Systematic Literature Review Comparing Intrasellar, Suprasellar, and Parasellar Locations

OBJECTIVE

Intracranial dermoid cyst (DC) is a rare benign, slow-growing lesion, most commonly arising along the midline. They can occur in the supratentorial compartment, very rarely involve the sellar region and only exceptionally are intrasellar. The aim of our study is to address the challenges in the diagnosis and management of sellar DCs.

METHODS

We performed a systematic review of sellar DCs, in keeping with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and described an intrasellar DC in a 32-year-old female who presented with bilateral blurring vision.

RESULTS

The review identified 4 intrasellar, 29 suprasellar, and 28 parasellar cases. Intrasellar DCs more likely present with progressive visual impairment and pituitary hormone dysfunctions during the fifth decade of life. Suprasellar and parasellar DCs are typically diagnosed during the third decade of life because of diplopia, ptosis, trigeminal hypoaesthesia/para-esthesia or cyst's rupture. Sellar DCs are typically hypodense on computed tomography scans and contain calcifications. Magnetic resonance imaging features include T1 hyperintensity, T2 heterogeneous intensity, no restriction on diffusion-weighted images, and no contrast enhancement. Surgery is the treatment of choice. Gross total resection is achieved in 60% of intrasellar and 61.9% of suprasellar and parasellar DCs. Early postoperative complications are reported in 40.0%, 16.7%, and 23.8% of intrasellar, suprasellar, and parasellar DCs, respectively.

CONCLUSIONS

Intrasellar DCs are rare lesions typically diagnosed later than suprasellar and parasellar DCs due to their different clinical presentations. However, they should be considered in the differential diagnosis of cystic lesions of the sella, including epidermoid cysts, craniopharyngiomas, Rathke's cleft cysts, and teratomas.

Myopathies of endocrine origin: A review for physicians

Myopathies are a common manifestation of endocrine disorders. Endocrine myopathies are often overlooked while considering differential diagnoses in patients with musculoskeletal symptoms. The hindrance to mobility and the musculoskeletal discomfort owing to these myopathies are important causes of disability and depreciated quality of life in these patients. Endocrine myopathies occur due to the effects of endogenous or iatrogenic hormonal imbalance on skeletal muscle protein and glucose metabolism, disrupting the excitation-contraction coupling. Abnormalities of the pituitary, thyroid, parathyroid, adrenal, and gonadal hormones have all been associated with myopathies and musculoskeletal symptoms. Endocrine myopathies can either be the complication of a secondary endocrine disorder or a presenting symptom of a missed underlying disorder. Therefore, an underlying endocrine abnormality must always be excluded in all patients with musculoskeletal symptoms. This review presents a compilation of various endocrine myopathies, their etiopathogenesis, clinical presentation, diagnostic modalities, and treatment protocols.

Adaptation of the Porcine Pituitary Transcriptome, Spliceosome and Editome during Early Pregnancy

The physiological mechanisms of the porcine reproduction are relatively well-known. However, transcriptomic changes and the mechanisms accompanying transcription and translation processes in various reproductive organs, as well as their dependence on hormonal status, are still poorly understood. The aim of this study was to gain a principal understanding of alterations within the transcriptome, spliceosome and editome occurring in the pituitary of the domestic pig (Sus scrofa domestica L.), which controls basic physiological processes in the reproductive system. In this investigation, we performed extensive analyses of data obtained by high-throughput sequencing of RNA from the gilts' pituitary anterior lobes during embryo implantation and the mid-luteal phase of the estrous cycle. During analyses, we obtained detailed information on expression changes of 147 genes and 43 long noncoding RNAs, observed 784 alternative splicing events and also found the occurrence of 8729 allele-specific expression sites and 122 RNA editing events. The expression profiles of the selected 16 phenomena were confirmed by PCR or qPCR techniques. As a final result of functional meta-analysis, we acquired knowledge regarding intracellular pathways that induce changes in the processes accompanying transcription and translation regulation, which may induce modifications in the secretory activity of the porcine adenohypophyseal cells.

The Emerging Role of m6A Modification in Endocrine Cancer

With the development of RNA modification research, N6-methyladenosine (m6A) is regarded as one of the most important internal epigenetic modifications of eukaryotic mRNA. It is also regulated by methylase, demethylase, and protein preferentially recognizing the m6A modification. This dynamic and reversible post-transcriptional RNA alteration has steadily become the focus of cancer research. It can increase tumor stem cell self-renewal and cell proliferation. The m6A-modified genes may be the primary focus for cancer breakthroughs. Although some endocrine cancers are rare, they may have a high mortality rate. As a result, it is critical to recognize the significance of endocrine cancers and identify new therapeutic targets that will aid in improving disease treatment and prognosis. We summarized the latest experimental progress in the m6A modification in endocrine cancers and proposed the m6A alteration as a potential diagnostic marker for endocrine malignancies.

Regional Growth Velocity and Incidence of Pancreatic Neuroendocrine Neoplasias in Multiple Endocrine Neoplasia Type 1

OBJECTIVES

Pancreatic neuroendocrine neoplasias (pNENs) in multiple endocrine neoplasia type 1 are predominantly found in the dorsal anlage. Whether their growth velocity and incidence might be related to their location in the pancreas has not been investigated yet.

METHODS

We studied 117 patients using endoscopic ultrasound.

RESULTS

Growth velocity could be calculated for 389 pNENs. Increase of largest tumor diameter (% per month) was 0.67 (standard deviation [SD], 2.04) in the pancreatic tail (n = 138), 1.12 (SD, 3.00) in the pancreatic body (n = 100), 0.58 (SD, 1.19) in the pancreatic head/uncinate process-dorsal anlage (n = 130), and 0.68 (SD, 0.77) in the pancreatic head/uncinate process-ventral anlage (n = 12). Comparing growth velocity of all pNENs in the dorsal (n = 368, 0.76 [SD, 2.13]) versus ventral anlage, no significant difference was detected. Annual tumor incidence rate was 0.21 in the pancreatic tail, 0.13 in the pancreatic body, 0.17 in the pancreatic head/uncinate process-dorsal anlage, 0.51 dorsal anlage together, and 0.02 in the pancreatic head/uncinate process-ventral anlage.

CONCLUSIONS

Multiple endocrine neoplasia type 1 pNENs are unequally distributed between ventral (low prevalence and incidence) and dorsal anlage. However, there are no regional differences in growth behavior.

Organizational Effects of Estrogens and Androgens on Estrogen and Androgen Receptor Expression in Pituitary and Adrenal Glands in Adult Male and Female Rats

Sex steroid hormones, such as androgens and estrogens, are known to exert organizational action at perinatal periods and activational effects during adulthood on the brain and peripheral tissues. These organizational effects are essential for the establishment of biological axes responsible for regulating behaviors, such as reproduction, stress, and emotional responses. Estradiol (E2), testosterone, and their metabolites exert their biological action through genomic and non-genomic mechanisms, bounding to canonical receptors, such as estrogen receptor (ER)α, ERβ, and androgen receptor (AR) or membrane receptors, such as the G protein-coupled estrogen receptor (GPER), respectively. Expression of ERs and AR was found to be different between males and females both in the brain and peripheral tissues, suggesting a sex-dependent regulation of their expression and function. Therefore, studying the ERs and AR distribution and expression levels is key to understand the central and peripheral role of sex steroids in the establishment of sex-specific behaviors in males and females. We investigated the organizational effects of estrogens and androgens in the pituitary and adrenal glands of adult male and female rats. For this, selective blockade of AR with flutamide or 5α-reductase with finasteride or aromatase with letrozole during the first 5 days of life has been performed in male and female pups and then quantification of ERs and AR expression in both glands has been carried out in adulthood. Data show that inhibition of dihydrotestosterone (DHT) and E2 production during the first five postnatal days mainly decreases the ER expression in male to female values and AR expression in female to male levels in the pituitary gland and increases AR expression in female to male levels in the adrenal gland. In contrast, blocking the action of androgens differentially modulates the ERs in males and females and decreases AR in both males and females in both glands. Altogether, the results suggest that neonatal modifications of the androgen and estrogen pathways can potentially lead to permanent modifications of the neuroendocrine functions of the pituitary and adrenal glands in the adulthood of both sexes.

Thyroid function and dysfunction in preterm infants-Challenges in evaluation, diagnosis and therapy

Thyroid hormone levels have a crucial role for optimal brain development from gestation through the first 2 postnatal years. However, thyroid hormones vary with gestational age, and their levels vary between term and preterm infants. Preterm newborns are prone to thyroid dysfunction which is now more frequently observed with the advances of neonatal care and improved survival of extremely premature infants. Thus, hypothyroxinaemia of prematurity associated with delayed TSH elevation is very common in low birth weight premature infants most likely due to the immaturity of the hypothalamic-pituitary thyroid axis. Furthermore, postnatal illness, medications and iodine status may contribute to the thyroid dysfunction or affect the interpretation of the thyroid function tests. Despite available guidelines, timing of screening and optimal treatment of thyroid dysfunction in premature infants remains controversial. Furthermore, it is unknown whether untreated thyroid dysfunction in premature babies affects neurodevelopmental outcome. In the vast majority of preterm infants, hypothyroxinaemia is transient; however, permanent hypothyroidism due to thyroid dysgenesis or enzyme defects might also occur. Therefore, careful monitoring of thyroid function and long-term follow-up is needed to assess an appropriate therapeutic approach. This article reviews thyroid physiology in preterm infants, the influences of gestation and other neonatal conditions on thyroid function tests, optimal timing of screening and possible predictors to differentiate transient hypothyroxinaemia from permanent hypothyroidism.

Pancreatic Neuroendocrine Neoplasias in Multiple Endocrine Neoplasia Type 1 Are Predominantly Located in the Dorsal Anlage: An Endoscopic Ultrasound Study

OBJECTIVES

Pancreatic neuroendocrine neoplasias (pNENs) frequently occur in multiple endocrine neoplasia type 1 (MEN1). Their distribution referring to embryology, that is, the pancreatic anlagen, has not been investigated yet.

METHODS

In the time between 1998 and 2019, we studied the distribution of pNENs in MEN1 concerning the embryologic origin of the pancreas, that is, the dorsal versus ventral anlage using endoscopic ultrasound in 117 MEN1 patients: 56 women, 61 men; aged 40 years (standard deviation, 14 years) at first endoscopic ultrasound.

RESULTS

In 105 patients, a total of 628 pNENs were detected. They were located in the pancreatic tail: 231; pancreatic body: 177; pancreatic head/uncinate process: 220. Of the latter, 22 were located in the ventral anlage, 176 in the dorsal anlage, and 22 remained undefined. In summary, just 3.5% of all detected pNENs were located in the ventral anlage, 93.0% in the dorsal anlage, and 3.5% could not be assigned.

CONCLUSIONS

Our study indicates that the vast majority of pNENs in MEN1 is located in the dorsal anlage, whereas the ventral anlage of the pancreas seems to be to a large extend spared from pNENs. Implications for new surgical strategies might be considered.

Neonatal Hypocalcemia in the Infant of a Diabetic Mother

Neonatal hypocalcemia (NHC) is one of the most common disorders of calcium metabolism in infants admitted to the NICU. Presentation can range from asymptomatic to generalized seizures or tetany. In this case study, an infant with NHC is presented along with an overview of the pathophysiology, prevalence, diagnosis, and management of NHC for neonatal clinicians.

Pituitary Adenomas: From Diagnosis to Therapeutics

Pituitary adenomas are tumors that arise in the anterior pituitary gland. They are the third most common cause of central nervous system (CNS) tumors among adults. Most adenomas are benign and exert their effect via excess hormone secretion or mass effect. Clinical presentation of pituitary adenoma varies based on their size and hormone secreted. Here, we review some of the most common types of pituitary adenomas, their clinical presentation, and current diagnostic and therapeutic strategies.

Endocrine Responses to Sport-Related Brain Injury in Female Athletes: A Narrative Review and a Call for Action

Sport-related brain injury (SRBI) occurs when a blow to the head causes the brain to move back and forth in the skull, and can lead to neuroendocrine dysfunction. Research has shown that males and females experience and recover from SRBI differently, yet most of what is known regarding diagnosis, treatment, and recovery of SRBI is based on male normative data even though females meet or exceed incidence numbers of SRBIs compared to those of males. Females also have been known to have worse outcomes and a greater number of symptoms following SRBI than males. Research is limited as to why females have worse outcomes, but sex hormones have been suggested as a potential reason. SRBI may cause a dysregulation of the hypothalamic–pituitary–gonadal (HPG) axis, which is responsible for regulating the sex hormones estrogen and progesterone. Initial research has shown that SRBI may suppress estrogen and progesterone, and the concentration of these sex hormones could be indicative of injury severity and recovery trajectory. This review discusses the sex-specific differences in SRBI and also the future direction of research that is needed in order to identify the repercussions of SRBIs for female athletes, which will eventually lead to better clinical treatment, sideline care, and recovery profiles.

The Hypothalamic-Pituitary-Adrenal Axis: Development, Programming Actions of Hormones, and Maternal-Fetal Interactions

The hypothalamic-pituitary-adrenal axis is a complex system of neuroendocrine pathways and feedback loops that function to maintain physiological homeostasis. Abnormal development of the hypothalamic-pituitary-adrenal (HPA) axis can further result in long-term alterations in neuropeptide and neurotransmitter synthesis in the central nervous system, as well as glucocorticoid hormone synthesis in the periphery. Together, these changes can potentially lead to a disruption in neuroendocrine, behavioral, autonomic, and metabolic functions in adulthood. In this review, we will discuss the regulation of the HPA axis and its development. We will also examine the maternal-fetal hypothalamic-pituitary-adrenal axis and disruption of the normal fetal environment which becomes a major risk factor for many neurodevelopmental pathologies in adulthood, such as major depressive disorder, anxiety, schizophrenia, and others.

Lateral fluid-percussion injury leads to pituitary atrophy in rats

Traumatic brain injury (TBI) causes neuroendocrine dysregulation in up to 40% of humans, which is related to impaired function of the hypothalamo-hypophyseal axis and contributes to TBI-related co-morbidities. Our objective was to investigate whether hypophyseal atrophy can be recapitulated in rat lateral fluid-percussion injury model of human TBI. High-resolution structural magnetic resonance images (MRI) were acquired from rats at 2 days and 5 months post-TBI. To measure the lobe-specific volumetric changes, manganese-enhanced MRI (MEMRI) scans were acquired from rats at 8 months post-TBI, which also underwent the pentylenetetrazol (PTZ) seizure susceptibility and Morris water-maze spatial memory tests. MRI revealed no differences in the total hypophyseal volume between TBI and controls at 2 days, 5 months or 8 months post-TBI. Surprisingly, MEMRI at 8 months post-TBI indicated a 17% reduction in neurohypophyseal volume in the TBI group as compared to controls (1.04 ± 0.05 mm3 vs 1.25 ± 0.05 mm3, p < 0.05). Moreover, neurohypophyseal volume inversely correlated with the number of PTZ-induced epileptiform discharges and the mean latency to platform in the Morris water-maze test. Our data demonstrate that TBI leads to neurohypophyseal lobe-specific atrophy and may serve as a prognostic biomarker for post-TBI outcome.

Ectopic pituitary adenomas: common presentations of a rare entity

PURPOSE

Ectopic pituitary adenomas (EPA) are rare tumors thought to arise from embryological remnants along the route of normal pituitary migration. Clinically, these tumors vary in hormonal activity and can exert mass effect based on location and size.

METHODS

We performed a single-center retrospective analysis of patients with diagnosis of ectopic pituitary adenoma from 2001 to 2018.

RESULTS

Five patients were identified with EPA: a 48-year-old woman with suprasellar EPA treated with transsphenoidal removal of the tumor, a 44-year-old woman with cavernous EPA treated with transsphenoidal removal of the tumor, a 48-year-old woman with sphenoid EPA treated with cabergoline, a 45-year-old man with clival EPA treated with cabergoline and transsphenoidal surgical resection, and a 54-year-old man with clival EPA treated with cabergoline therapy.

CONCLUSIONS

EPA should be considered as a differential diagnosis of juxta-sellar lesions. Appropriate hormonal testing may lead to early diagnosis, avoidance of unnecessary biopsy or surgery, and improved outcomes.

Lack of Ubiquitin Specific Protease 8 (USP8) Mutations in Canine Corticotroph Pituitary Adenomas

Purpose

Cushing’s disease (CD), also known as pituitary-dependent hyperadrenocorticism, is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary tumours. Affected humans and dogs have similar clinical manifestations, however, the incidence of the canine disease is thousand-fold higher. This makes the dog an obvious model for studying the pathogenesis of pituitary-dependent hyperadrenocorticism. Despite certain similarities identified at the molecular level, the question still remains whether the two species have a shared oncogenetic background. Recently, hotspot recurrent mutations in the gene encoding for ubiquitin specific protease 8 (USP8) have been identified as the main driver behind the formation of ACTH-secreting pituitary adenomas in humans. In this study, we aimed to verify whether USP8 mutations also play a role in the development of such tumours in dogs.

Methods

Presence of USP8 mutations was analysed by Sanger and PCR-cloning sequencing in 38 canine ACTH-secreting adenomas. Furthermore, the role of USP8 and EGFR protein expression was assessed by immunohistochemistry in a subset of 25 adenomas.

Results

None of the analysed canine ACTH-secreting adenomas presented mutations in the USP8 gene. In a subset of these adenomas, however, we observed an increased nuclear expression of USP8, a phenotype characteristic for the USP8 mutated human tumours, that correlated with smaller tumour size but elevated ACTH production in those tumours.

Conclusions

Canine ACTH-secreting pituitary adenomas lack mutations in the USP8 gene suggesting a different genetic background of pituitary tumourigenesis in dogs. However, elevated nuclear USP8 protein expression in a subset of tumours was associated with a similar phenotype as in their human counterparts, indicating a possible end-point convergence of the different genetic backgrounds in the two species. In order to establish the dog as a useful animal model for the study of CD, further comprehensive studies are needed.

MR Imaging of the Pituitary Gland and Postsphenoid Ossification in Fetal Specimens

BACKGROUND AND PURPOSE

A thorough knowledge of fetal growth and development is key to understanding both the normal and abnormal fetal MR imaging findings. We investigated the size and signal intensity of the normal pituitary gland and the intrasphenoidal ossification around the Rathke pouch in formalin-fixed fetuses on MR imaging.

MATERIALS AND METHODS

Thirty-two fetuses with undamaged brains were included in this study (mean age, 19.93 weeks; age range, 12-31 weeks). Visual inspection of the pituitary and ossification around the Rathke pouch in the sphenoid bone or the postsphenoid ossification was conducted. The extent of pituitary and postsphenoid ossification, pituitary/pons signal ratio, and postsphenoidal ossification/sphenoid bone signal ratio was compared according to gestational age.

RESULTS

The pituitary gland was identified as a hyperintense intrasellar structure in all cases, and postsphenoid ossification was identified as an intrasphenoidal hyperintense area in 27 of the 32 cases (84%). The mean pituitary/pons signal ratio was 1.13 ± 0.18 and correlated weakly with gestational age (R(2) = 0.243), while the mean postsphenoid ossification/sphenoid bone signal ratio was 2.14 ± 0.56 and did not show any increase with gestational age (R(2) = 0.05). No apparent change in the size of pituitary hyperintensity was seen with gestational age (R(2) = 0.001). Postsphenoid ossification showed an increase in size with gestational age (R(2) = 0.307).

CONCLUSIONS

The fetal pituitary gland was hyperintense on T1-weighted images and the pituitary/pons ratio and extent of postsphenoid ossification correlated weakly with gestational age.

Nonsocial functions of hypothalamic oxytocin

Oxytocin (OXT) is a hypothalamic neuropeptide composed of nine amino acids. The functions of OXT cover a variety of social and nonsocial activity/behaviors. Therapeutic effects of OXT on aberrant social behaviors are attracting more attention, such as social memory, attachment, sexual behavior, maternal behavior, aggression, pair bonding, and trust. The nonsocial behaviors/functions of brain OXT have also received renewed attention, which covers brain development, reproduction, sex, endocrine, immune regulation, learning and memory, pain perception, energy balance, and almost all the functions of peripheral organ systems. Coordinating with brain OXT, locally produced OXT also involves the central and peripheral actions of OXT. Disorders in OXT secretion and functions can cause a series of aberrant social behaviors, such as depression, autism, and schizophrenia as well as disturbance of nonsocial behaviors/functions, such as anorexia, obesity, lactation failure, osteoporosis, diabetes, and carcinogenesis. As more and more OXT functions are identified, it is essential to provide a general view of OXT functions in order to explore the therapeutic potentials of OXT. In this review, we will focus on roles of hypothalamic OXT on central and peripheral nonsocial functions.

Episodes of prolactin gene expression in GH3 cells are dependent on selective promoter binding of multiple circadian elements

Prolactin (PRL) gene expression in mammotropes occurs in pulses, but the mechanism(s) underlying this dynamic process remains obscure. Recent findings from our laboratory of an E-box in the rat PRL promoter (E-box133) that can interact with the circadian factors, circadian locomoter output cycles kaput (CLOCK) and brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein (BMAL)-1, and was necessary for pulse activity raised the intriguing possibility that the circadian system may be central to this oscillatory process. In this study, we used serum-shocked GH(3) cells, established previously to synchronize PRL pulses between cells in culture, to reveal that pulses of PRL mRNA are linked temporally to the expression of bmal1, cry1, per1, and per3 mRNA in these cells. Moreover, we found that each of these circadian factors binds to the rat PRL promoter by chromatin immunoprecipitation analysis. Using EMSA analysis, we observed that two sites present in the proximal promoter region, E-box133 and E-box10, bind circadian factors differentially (E-box133 interacted with BMAL1, cryptochrome-1, period (PER)-1, and PER3 but not PER2 and E-box10 bound BMAL1, cryptochrome-1, PER2, PER3 but not PER1). More importantly, down-regulation of any factor binding E-box133 significantly reduced PRL mRNA levels during pulse periods. Our results demonstrate clearly that certain circadian elements binding to the E-box133 site are required for episodes of PRL mRNA expression in serum-shocked GH(3) cultures. Moreover, our findings of binding-related differences between functionally distinct E-boxes demonstrate not only that E-boxes can bind different components but suggest that the number and type of circadian elements that bind to an E-box is central in dictating its function.

Ultrastructural and immunohistochemical characteristics of developing human pituitary gland

The development and differentiation of the human pituitary gland and its relationship to other structures of the head were analysed in nine human embryos and fetuses aged 5-10 weeks old using morphological and immunohistochemical methods. In the 5th developmental week, the primordium of Rathke's pouch was closely associated with the cranial tip of the notochord, head mesenchyme and diencephalon. Cells of the Rathke's pouch displayed typical epithelial features that transformed into gland-like structures during development. Numerous Ki-67 positive cells characterised the Rathke's pouch, the diencephalon (neurohypophysis) and the associated mesenchyme. The highest proliferation rate was noticed in the earliest developmental stage, while it significantly decreased in the 7th week of development. The first intermediate filaments to appear in the Rathke's pouch showed cytokeratin 8 immunolabelling which decreased with advanced maturation. The diencephalon and infundibulum displayed parallel immunolabelling of vimentin, glial fibrillary acidic protein (GFAP) and neurofilament protein (NF), while the surrounding mesenchyme showed only vimentin labelling. Changes in the labelling of Ki-67 proliferation marker and intermediate filament proteins in the developing human pituitary gland coincided with separation of the Rathke's pouch from the pharyngeal epithelium and subsequent differentiation of different parts of the gland.

Pituitary gland: development, normal appearances, and magnetic resonance imaging protocols

In this article, I will review the normal anatomy of the pituitary gland starting with a brief review of aspects of its origin and development that are pertinent to radiologists. The anatomy of the anterior and posterior lobes will be addressed as will be that of the surrounding structures and of the vascular structures of the gland. Radiologists need to be familiar with the normal magnetic resonance imaging appearance of the gland and the changes that it undergoes throughout life. The normal patterns of contrast enhancement by the gland are described. Normal pituitary variations and incidental conditions are discussed, and the article finishes by describing appropriate imaging protocols.

Tumeurs endocrines : biologie et physiopathologie

Endocrine tumors are defined as neoplastic lesions resulting from the proliferation of cells engaged in an endocrine differentiation pathway, as shown by their expression of a set of specific markers, including true endocrine markers (such as chromogranine A) and neuro-endocrine markers, shared between neurons and endocrine cells (such as synaptophysin). The demonstration of the synthesis and secretion of one or several hormones is not necessary for the assessment of the endocrine nature of a tumor; only tumors associated with a clinical syndrome resulting from hormone overproduction can be said functioning endocrine tumors. Beyond their common features, endocrine tumors are characterized by a marked diversity, which results from the large functional, structural and embryological heterogeneity of normal endocrine cells. The natural history of endocrine tumors is also characterized by a marked heterogeneity in their evolution and rate of progression. While most endocrine tumors are locally and slowly evolving, some of them behave as truly malignant tumors, as shown by their capacity of metastatic dissemination and their fatal evolution. A better understanding of the cellular and molecular mechanisms involved in tumor progression and metastatic dissemination is necessary for the identification of new prognostic tools and novel therapeutic targets.

Zac1 is expressed in progenitor/stem cells of the neuroectoderm and mesoderm during embryogenesis: differential phenotype of the Zac1-expressing cells during development

Zac1, a new zinc-finger protein that regulates both apoptosis and cell cycle arrest, is abundantly expressed in many neuroepithelia during early brain development. In the present work, we study the expression of Zac1 during early embryogenesis and we determine the cellular phenotype of the Zac1-expressing cells throughout development. Our results show that Zac1 is expressed in the progenitor/stem cells of several tissues (nervous system, skeleton, and skeletal muscle), because they colocalize with several progenitor/stem markers (Nestin, glial fibrillary acidic protein, FORSE-1, proliferating cell nuclear antigen, and bromodeoxyuridine). In postnatal development, Zac1 is expressed in all phases of the life cycle of the chondrocytes (from proliferation to apoptosis), in some limbic gamma-aminobutyric acid-ergic neuronal subpopulations, and during developmental myofibers. Therefore, the intense expression of Zac1 in the progenitor/stem cells of different cellular lineages during the proliferative cycle, before differentiation into postmitotic cells, suggests that Zac1 plays an important role in the control of cell fate during neurogenesis, chondrogenesis, and myogenesis.

Pulses of prolactin promoter activity depend on a noncanonical E-box that can bind the circadian proteins CLOCK and BMAL1

Recent findings from our laboratory and those of others demonstrated that prolactin gene expression (PRL-GE) oscillates in single living mammotropes, but little information is available on the molecular processes that contribute to this phenomenon. To elucidate the source of this activity, we generated a series of constructs containing decreasing lengths of the PRL promoter fused to a luciferase reporter gene. These constructs were injected into single cells and assayed for photonic activity. We found pulse activity with all plasmids tested, even with the smallest promoter fragment of 331 bp. Sequence analysis of this fragment identified two potential E-boxes (elements known to bind CLOCK and BMAL1 circadian proteins). Furthermore, RT-PCR of PRL cells (pituitary, MMQ, and GH(3)) revealed expression of clock and bmal1 as well as five other clock genes (per1, per2, cry1, cry2, and tim), suggesting that the circadian system may function in PRL cells. Next, we mutated the core sequences of both E-boxes within the 2.5-kb PRL promoter and found that only mutation of the E-box133 completely abolished PRL-GE pulses. EMSAs revealed that CLOCK and BMAL1 were able to bind to the E-box133 site in vitro. Our results demonstrate that PRL-GE pulses are dependent on a specific E-box binding site in the PRL promoter. Moreover, the indication that CLOCK/BMAL1 can bind to this site suggests that these circadian proteins, either alone or in conjunction with other factors, may regulate intermittent PRL promoter activity in mammotropes, perhaps by acting as a temporal switch for the on/off expression of PRL.

Glutamate signaling in peripheral tissues

The hypothesis that l-glutamate (Glu) is an excitatory amino acid neurotransmitter in the mammalian central nervous system is now gaining more support after the successful cloning of a number of genes coding for the signaling machinery required for this neurocrine at synapses in the brain. These include Glu receptors (signal detection), Glu transporters (signal termination) and vesicular Glu transporters (signal output through exocytotic release). Relatively little attention has been paid to the functional expression of these molecules required for Glu signaling in peripheral neuronal and non-neuronal tissues; however, recent molecular biological analyses show a novel function for Glu as an extracellular signal mediator in the autocrine and/or paracrine system. Emerging evidence suggests that Glu could play a dual role in mechanisms underlying the maintenance of cellular homeostasis - as an excitatory neurotransmitter in the central neurocrine system and an extracellular signal mediator in peripheral autocrine and/or paracrine tissues. In this review, the possible Glu signaling methods are outlined in specific peripheral tissues including bone, testis, pancreas, and the adrenal, pituitary and pineal glands.

Genetic analysis of adenohypophysis formation in zebrafish

The adenohypophysis consists of at least six different cell types, somatotropes, lactotropes, thyrotropes, melanotropes, corticotropes, and gonadotropes. In mouse, cloning of spontaneous mutations and gene targeting has revealed multiple genes required for different steps of adenohypophysis development. Here, we report the results of a systematic search for genes required for adenohypophysis formation and patterning in zebrafish. By screening F3 offspring of N-ethyl-N-nitrosourea-mutagenized founder fish, we isolated eleven mutants with absent or reduced expression of GH, the product of somatotropes, but a normally developing hypothalamus. Of such mutants, eight were further analyzed and mapped. They define four genes essential for different steps of adenohypophysis development. Two of them, lia and pia, affect the entire adenohypophysis, whereas the other two are required for a subset of adenohypophyseal cell types only. The third gene is zebrafish pit1 and is required for lactotropes, thyrotropes, and somatotropes, similar to its mouse ortholog, whereas the fourth, aal, is required for corticotropes, melanotropes, thyrotropes, and somatotropes, but not lactotropes. In conclusion, the isolated zebrafish mutants confirm principles of adenohypophysis development revealed in mouse, thereby demonstrating the high degree of molecular and mechanistic conservation among the different vertebrate species. In addition, they point to thus far unknown features of adenohypophysis development, such as the existence of a new lineage of pituitary cells, which partially overlaps with the Pit1 lineage. Positional cloning of the lia, pia, and aal genes might reveal novel regulators of vertebrate pituitary development.