Majority Of Pituitary Adenomas Research Articles

Expression of Peroxisome Proliferator-Activated Receptor Alpha (PPARα) in Non-Somatotroph Pituitary Tumours and the Effects of PPARα Agonists on MMQ Cells

Peroxisome proliferator-activated receptor alpha (PPARα) has been involved in the regulation of somatotroph tumour cells and may be targeted by different drugs, some of them are in current clinical use. The aim of this study was to investigate the expression of PPARα in additional phenotypes of pituitary adenomas (PA), the relationship between PPARα and its potential molecular partner aryl hydrocarbon receptor interacting protein (AIP) in these tumours, and the effects of PPARα agonists on lactotroph cells. Seventy-five human PA - 57 non-functioning (NFPA) and 18 prolactinomas (PRL-PA) - were characterised for PPARα and AIP expression by real time RT-PCR and/or immunohistochemistry (IHC), and the effects of fenofibrate and WY 14 643 on MMQ cells were studied in vitro. PPARα was expressed in a majority of PA. PPARα immunostaining was observed in 93.7% PRL-PA vs. 60.6% NFPA (p=0.016), the opposite being found for AIP (83.3% in NFPA vs. 43.7% in PRL-PA, p=0.003). PPARα expression was unrelated to gonadotroph differentiation in NFPA, but positively correlated with tumour volume in PRL-PA. Both drugs significantly reduced MMQ cell growth at high concentrations (100-200 μM). At the same time, despite modest stimulating effects on PRL secretion were observed, these were overcome by the reduction in cell number. In conclusion, PPARα is commonly expressed by PRL-PA and NFPA, regardless of AIP, and may represent a new target of PPARα agonists.

Prothymosin-alpha and Ki-67 expression in pituitary adenomas.

Prothymosin alpha (PTMA), a nuclear oncoprotein involved in cell cycle regulation, is used as a prognostic marker in many cancers. The histopathology of pituitary carcinomas and locally invasive adenomas is indistinguishable from that of benign tumors. A new marker is needed to differentiate these lesions. We evaluated PTMA in pituitary adenomas to determine its usefulness as a prognostic factor of tumor proliferation. We conducted a retrospective analysis of a group of 27 patients, including 15 females (56%) and 12 males (44%) with a mean age of 58.6±12 years, who underwent pituitary tumor surgery between 2003 and 2012. The Ki-67 and PTMA-nuclear (PTMA-n) and PTMA-cytoplasmic (PTMA-c) indices were determined by immunohistochemical staining. We studied histopathological features, clinical symptoms, and magnetic resonance imaging or computed tomography performed before surgery and one year following surgery to evaluate tumor size and progression. The expression of Ki-67 was revealed in 77.8% of adenomas, PTMA-n in 81.5% and PTMA-c in 92.6%. The mean value of the Ki-67 index was 1.8%, PTMA-n was 1.84%, and PTMA-c was 35.6%. There was a significant positive correlation between Ki-67 and PTMA-n (p=0.009). We did not find any correlation between Ki-67, PTMA-c, and tumor progression. PTMA-n was found to be correlated with tumor size (p=0.045) and was higher in the case of gonadotropinomas (p=0.026). The positive nuclear expression of Ki-67 and PTMA was observed in the majority of pituitary adenomas. Neither the expression of Ki-67 nor that of PTMA-c was related to tumor recurrence or local invasion.

Study of the Involvement of Pancreastatin in the Physiopathology of Diabetes Mellitus Associated with Nonsecreting Pituitary Adenomas

Pancreastatin, derived from chromogranin A, inhibits insulin and stimulates glucagon secretion in rodents. Immunohistochemistry localised pancreastatin in human pancreatic islet cells and gonadotroph pituitary cells. Nonsecreting pituitary adenomas, frequently associated with diabetes mellitus, arise quasi-constantly from gonadotroph cells. We evaluated the possible involvement of pancreastatin in the physiopathology of diabetes mellitus associated with nonsecreting pituitary adenomas. Plasma pancreastatin levels were measured by radioimmunoassay in 5 groups of subjects: 10 patients with nonsecreting pituitary adenomas associated with diabetes mellitus (group I), 10 patients with nonsecreting pituitary adenomas without diabetes (Group II), 10 patients with ACTH or GH-secreting pituitary adenomas and diabetes mellitus (Group III), 10 diabetic patients without pituitary adenomas (Group IV), and 10 healthy controls (Group V). Kidney and liver functions were normal in all of them and no patient was treated with a proton pump inhibitor. All pituitary adenomas were trans-sphenoidally removed. Immunohistochemistry against pancreastatin was performed in 5 patients of each of the 3 groups of pituitary adenomas. Plasma pancreastatin levels were not different between the different groups: 182±46 pg/ml (Group I), 195±57 pg/ml (Group II), 239±42 pg/ml (Group III), 134±31 pg/ml, (Group IV), and 122±29 pg/ml (Group V). In contrast, they were significantly (p<0.05) higher before (391±65 pg/ml) than after trans-sphenoidal surgery (149±18 pg/ml) without post-surgical change in diabetes. An immunostaining against pancreastatin was found in a majority of pituitary adenomas, associated or not with diabetes mellitus. These results argue against a role of pancreastatin in the pathogenesis of diabetes mellitus associated with nonsecreting pituitary adenomas.

Reassessment of sst3 Somatostatin Receptor Expression in Human Normal and Neoplastic Tissues Using the Novel Rabbit Monoclonal Antibody UMB-5

Background: Among the five somatostatin receptors (sst₁-sst₅), the sst₃ receptor displays a distinct pharmacological profile. Like sst₂, the sst₃ receptor efficiently internalizes radiolabeled somatostatin analogs. Unlike sst₂, however, internalized sst₃ receptors are rapidly transferred to lysosomes for degradation. Apart from this, very little is known about the clinical relevance of the sst₃ receptor, which may in part be due to the lack of specific monoclonal sst₃ antibodies. Methods: Here, we have extensively characterized the novel rabbit monoclonal anti-human sst₃ antibody UMB-5 using transfected cells and receptor-expressing tissues. UMB-5 was then subjected to immunohistochemical staining of a series of 190 formalin-fixed, paraffin-embedded normal and neoplastic human tissues. Results: Specificity of UMB-5 was demonstrated by detection of a broad band migrating at a molecular weight of 70,000–85,000 in immunoblots from human pituitary. After enzymatic deglycosylation, the size of this band decreased to a molecular weight of 45,000. Tissue immunostaining was completely abolished by pre-adsorption of UMB-5 with its immunizing peptide. In addition, UMB-5 detected distinct cell populations in human tissues like pancreatic islands, anterior pituitary, adrenal cortex, adrenal medulla, and enteric ganglia, similar to that seen with a rabbit polyclonal antibody generated against a different carboxyl-terminal epitope of the sst₃ receptor. In a comparative immunohistochemical study, UMB-5 yielded predominant plasma membrane staining in the majority of pituitary adenomas, pheochromocytomas, and a subset of neuroendocrine tumors. The sst₃ receptor was also present in many glioblastomas, pancreatic, breast, cervix, and ovarian carcinomas. Conclusion: The rabbit monoclonal antibody UMB-5 may prove of great value in the identification of sst₃-expressing tumors during routine histopathological examinations. Given its unique trafficking properties, these tumors may be potential candidates for sst₃-directed receptor radiotherapy.

The genetics of pituitary adenomas

Pituitary adenomas are one of the most frequent intracranial tumors with a prevalence of clinically-apparent tumors close to 1:1000 of the general population. They are clinically significant because of hormone overproduction and/or tumor mass effects in addition to the need for neurosurgery, medical therapies and radiotherapy. The majority of pituitary adenomas have a sporadic origin with recognized genetic mutations seldom being found; somatotropinomas are an exception, presenting frequent somatic GNAS mutations. In this and other phenotypes, tumorigenesis could possibly be explained by altered function of genes implicated in cell cycle regulation, growth factors or their receptors, cell-signaling pathways, specific hormonal factors or other molecules with still unclear mechanisms of action. Genetic changes, such as allelic loss or gene amplification, and epigenetic changes, usually by promoter methylation, have been implicated in abnormal gene expression, but alternative mechanisms may be present. Familial cases of pituitary adenomas represent 5% of all pituitary tumors. MEN1 mutations cause multiple endocrine neoplasia type 1 (MEN1), while the Carney complex (CNC) is characterized by mutations in the protein kinase A regulatory subunit-1alpha (PRKAR1A) gene or changes in a locus at 2p16. Recently, a MEN1-like condition, MEN4, was found to be related to mutations in the CDKN1B gene. The clinical entity of familial isolated pituitary adenomas (FIPA) is characterized by genetic defects in the aryl hydrocarbon receptor interacting protein (AIP) gene in about 15% of all kindreds and 50% of homogenous somatotropinoma families. Identification of familial cases of pituitary adenomas is important as these tumors may be more aggressive than their sporadic counterparts.

The epidemiology and genetics of pituitary adenomas

According to data derived from autopsy and radiological imaging series, pituitary tumours occur very commonly in the general population; however, most of these tumours are incidental findings with no obvious clinical impact. The historical data on the prevalence of pituitary adenomas in the clinical setting are scant and point to such tumours being relatively rare. Recent studies have shown that the prevalence of clinically relevant pituitary adenomas is 3-5 times higher than previously reported, which adds impetus to research into the aetiology of these tumours. Although the majority of pituitary adenomas are sporadic, approximately 5% of all cases occur in a familial setting and over half of these are due to Multiple Endocrine Neoplasia Type 1 (MEN-1) and Carney's Complex (CNC) disorders. Since the late 1990 s, we have described non-MEN1/CNC familial pituitary tumours that include all tumour phenotypes as a condition termed Familial Isolated Pituitary Adenomas (FIPAs). The clinical characteristics of the FIPAs vary from those sporadic pituitary adenomas, as patients with FIPAs have a younger age at diagnosis and larger tumours. About 15% of the FIPA patients have mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP), which indicates that the FIPA may have a diverse genetic pathophysiology.

Beta human chorionic gonadotropin (β-hCG) expression in pituitary adenomas: relationship to endocrine function and tumour recurrence

The beta subunit of human chorionic gonadotropin (beta-hCG) is a marker of malignancies. Recent studies have also reported its expression in pituitary adenomas, although its significance is unclear. In this retrospective study, the authors quantitatively investigated the immunohistochemical expression of beta-hCG in 123 patients undergoing surgery for pituitary adenomas and explored its relationship to the rest of the endocrine function, tumour recurrence and Ki-67 nuclear labelling. Based on the endocrine profile and immunohistochemistry, the pituitary adenomas were grouped into non-functioning (NFPA; N = 78) and functioning pituitary adenomas (N = 45). The latter included, 20 growth hormone (GH), 12 prolactin (PRL), 8 adreno-corticotrophin hormone (ACTH) and 5 mixed GH-PRL-producing adenomas. Ninety-three (76%) tumours were classified as primary and 30 (24%) tumours classified as recurrent adenomas. Immunohistochemically, 107 (87%) of pituitary adenomas expressed beta-hCG, which was more common in NFPA (91%) than functioning pituitary adenomas (80%). beta-hCG expression was not different between primary (86%) and recurrent pituitary adenomas (90%) and it was also not related to raised Ki-67 labelling. But, Ki-67 labelling was raised in recurrent pituitary adenomas (33%), compared to primary pituitary adenomas (11%). Although, beta-hCG is expressed in the majority of pituitary adenomas, more especially in NFPA, it is un-related to the risk of tumour recurrence or cellular proliferation as measured by Ki-67 nuclear labelling. The high incidence of beta-hCG expression in pituitary adenomas may provide a target for specific beta-hCG-directed tumour therapies in the future.

Abundant hypermethylation of SOCS-1 in clinically silent pituitary adenomas

Janus kinase (JAK)/signal transducers and activators of transcription (STAT) cascade are required for cytokines, growth factors, G-proteins and hormones (growth hormone and prolactin). Gatekeepers in this pathway are the suppressor of cytokine signalling (SOCS) family of proteins. Their expression level is epigenetically regulated by DNA methylation. We have investigated the CpG island methylation status of SOCS-1 in a cohort of pituitary adenomas (PA; n=57), craniopharyngiomas (CP; n=30) and normal pituitary tissue (NP; n=11) using methylation sensitive single-strand conformation polymorphism analysis (MS-SSCP) and direct sequencing. SOCS-1 hypermethylation was identified in 51% (29/57) of surgical specimens obtained from PA patients. 83% of these tumours were clinically silent. In contrast, no methylation of SOCS-1 was observed in CPs or NPs. Quantitative real-time PCR and western blot analysis confirmed reduced SOCS-1 expression in the majority of pituitary adenomas. The data is compatible with epigenetic silencing of the SOCS-1 gene and constitutive activation of the JAK-STAT pathway in PA. This appears to contribute particularly to those tumours characterized by a hormone-inactive status.

Apathy and Pituitary Disease: It Has Nothing to Do With Depression

Increasingly, patients with pituitary disease are evaluated and treated at cancer centers. In many ways, these patients resemble patients with other malignant brain tumors. Although the majority of pituitary adenomas are benign, the physical, emotional, and cognitive changes that these patients experience on their well-being is malignant. Pituitary disease causes a variety of physical illnesses resulting from the alterations in the hypothalamic-pituitary-end organ axis. In addition, patients with pituitary diseases may experience many emotional problems, including depression, anxiety, behavioral disturbances, and personality changes, above and beyond the many reactions these patients may have to the myriad of adjustments that they must make in their lives. There is a growing understanding that pituitary patients may experience these emotional problems as a result of long-term effects that the pituitary tumor itself, treatment, and/or hormonal changes have on the hypothalamic-pituitary-end organ axis. The authors present a series of cases, in which patients with pituitary disease were diagnosed and treated for depression and showed little response to the treatment for depression. When the diagnosis of apathy syndrome was considered and treatment implemented, the patients’ condition improved. A review of the literature on apathy, hypothalamic-pituitary-end organ axis dysfunction, and treatment for apathy syndrome is included.

Apathy and Pituitary Disease: It Has Nothing to Do With Depression

Increasingly, patients with pituitary disease are evaluated and treated at cancer centers. In many ways, these patients resemble patients with other malignant brain tumors. Although the majority of pituitary adenomas are benign, the physical, emotional, and cognitive changes that these patients experience on their well-being is malignant. Pituitary disease causes a variety of physical illnesses resulting from the alterations in the hypothalamic-pituitary-end organ axis. In addition, patients with pituitary diseases may experience many emotional problems, including depression, anxiety, behavioral disturbances, and personality changes, above and beyond the many reactions these patients may have to the myriad of adjustments that they must make in their lives. There is a growing understanding that pituitary patients may experience these emotional problems as a result of long-term effects that the pituitary tumor itself, treatment, and/or hormonal changes have on the hypothalamic-pituitary-end organ axis. The authors present a series of cases, in which patients with pituitary disease were diagnosed and treated for depression and showed little response to the treatment for depression. When the diagnosis of apathy syndrome was considered and treatment implemented, the patients' condition improved. A review of the literature on apathy, hypothalamic-pituitary-end organ axis dysfunction, and treatment for apathy syndrome is included.

Loss of expression of the growth inhibitory gene GADD45gamma, in human pituitary adenomas, is associated with CpG island methylation.

Inappropriate expression of cell-cycle regulatory genes and/or their protein products are a frequent finding in pituitary tumours; however, genetic changes associated with or responsible for their dysregulation are in general uncommon. In a search for novel genes, and employing cDNA-representational difference analysis, the gene encoding GADD45gamma was recently isolated and identified as being under-represented in pituitary adenomas. GADD45gamma is a member of a family of genes that are induced by DNA damage and function in the negative regulation of cell growth. In this study, we further confirm this initial report that the majority of pituitary adenomas (22 of 33; 67%) do not express GADD45gamma as determined by RT-PCR analysis. Loss of expression was not associated with either loss of heterozygosity or mutations within the coding region of this gene. In marked contrast, epigenetic change, namely methylation of the GADD45gamma genes CpG island, was a frequent finding (19 of 33 adenoma; 58%) and was significantly associated with tumours in which GADD45gamma transcript was not expressed (18 of 22; 82%; P=0.002). In common with the primary tumours, methylation-associated gene silencing of the GADD45gamma gene was also found in the pituitary tumour cell line AtT20. The treatment of AtT20 cells with the demethylating agent, 5-Aza-2'-deoxycytidine, induced the re-expression of this gene. These findings show that silencing of the GADD45gamma gene in pituitary tumours is primarily associated with methylation of the genes CpG island. Methylation has functional importance since reversal of this epigenetic change in a pituitary-derived cell line is associated with re-expression. Silencing of GADD45gamma, a negative regulator of cell growth, is most likely responsible for conferring a selective growth advantage during tumour evolution and outgrowth.

Targeted overexpression of luteinizing hormone causes ovary-dependent functional adenomas restricted to cells of the Pit-1 lineage.

The majority of pituitary adenomas in humans are nonmetastasizing, monoclonal neoplasms that occur in approximately 20% of the general population. Their development has been linked to a combination of extrinsic factors and intrinsic defects. We now demonstrate with transgenic mice that targeted and chronic overexpression of LH causes ovarian hyperstimulation and subsequent hyperproliferation of Pit-1-positive cells that culminates in the appearance of functional pituitary adenomas ranging from focal to multifocal expansion of lactotropes, somatotropes, and thyrotropes. Tumors fail to develop in ovariectomized mice, indicating that contributions from the ovary are necessary for adenoma development. Although the link between chronic ovarian hyperstimulation and PRL-secreting adenomas was expected, the involvement of somatotropes and thyrotropes was surprising and suggests that multiple ovarian hormones may contribute to this unusual pathological consequence. In support of this idea, we have found that ovariectomy followed by estrogen replacement results in the expansion of lactotropes selectively in LH overexpressing mice, but not somatotropes and thyrotropes. Collectively, these data indicate that estrogen is sufficient for the formation of lactotrope adenomas only in animals with a hyperstimulated ovary, whereas the appearance of GH- and TSH-secreting adenomas depends on multiple ovarian hormones. Together, our data expand current models of pituitary tumorigenesis by suggesting that chronic ovarian hyperstimulation may underlie the formation of a subset of pituitary adenomas containing lactotropes, somatotropes, and thyrotropes.

Anaesthesia for pituitary surgery

Surgical lesions of the pituitary gland, the majority of which are benign adenomas of the anterior lobe, present a varied and challenging spectrum of peri-operative anaesthetic problems. Successful management is based on a comprehensive understanding of the applied anatomy and physiology of the pituitary gland, the endocrine and neurosurgical consequences of pituitary adenomas and the specific implications of the chosen neurosurgical approach. The majority of pituitary adenomas can be resected adequately by an extracranial trans-sphenoidal approach, although transcranial resection may be necessary if the tumour has a significant suprasellar extension or if the diagnosis is in doubt. In general terms, pituitary surgery demands the same levels of peri-operative care as those required by intracranial surgery.

Hpttg is over-expressed in pituitary adenomas and other primary epithelial neoplasias.

The role of oncogenes in pituitary tumorigenesis remains elusive since few genetic changes have been identified so far in pituitary tumors. Pituitary tumor-transforming gene (pttg) has been recently cloned from rat GH4 pituitary tumor cells. We have previously isolated and characterized hpttg from human thymus. In the present study, we analyse the expression of hpttg mRNA in a series of human pituitary adenomas. We show that hpttg is highly expressed in the majority of pituitary adenomas while only very low levels of mRNA can be detected in normal pituitary gland by Northern blot analysis. hPTTG protein was immunolocalized mainly in the cytoplasm of adenoma cells. Other common extra-cranial malignant tumors were also analysed by immunohistochemistry. Interestingly, strong hPTTG immunoreactivity was detected in most adenocarcinomas of mammary and pulmonary origins.

Expression of von Hippel-Lindau protein (VHL-P) in nontumorous and adenomatous human pituitaries.

We studied the presence of von Hippel-Lindau protein (VHL-P) in 7 nontumorous pituitaries and 68 pituitary adenomas by immunocytochemistry using a polyclonal antibody which detects both normal and mutated forms. In nontumorous pituitary VHL-P was variable expressed in the cytoplasm of most adenohypophysial cells. In addition, weak diffuse staining was noted in the posterior lobe. Among the 53 VHL-P immunopositive adenomas (78%), 32 showed only cytoplasmic, 7 only nuclear, and 14 both cytoplasmic and nuclear immunoreactivity. In densely (8 cases) and sparsely (7 cases) granulated somatotroph adenomas nuclear and weak cytoplasmic immunoreactivity were common; all 4 sparsely granulated lactotroph adenomas had only moderate cytoplasmic immunostaining; all 7 functioning corticotroph adenomas presented intense cytoplasmic immunoreactivity and 4/7 showing nuclear immunostaining as well; all 3 silent subtype 1 adenomas were negative; 7 3/4 silent subtype 2 and 4/7 silent subtype 3 adenomas exhibited only cytoplasmic immunoreactivity; thyrotroph adenomas showed variable patterns from negative in 1/7, to only cytoplasmic in 2/7, nuclear alone in 2/7, or both in 2/7. Only weak, focal cytoplasmic immunoreactivity was noted in gonadotroph adenomas of female (2/4) and male (1/5) type. Lastly, all 4 null cell and 8 oncocytic adenomas showed moderate to intense cytoplasmic immunoreactivity. It can be concluded that the majority of pituitary adenomas express the VHL-P with variable distributions and intensity in different tumor types. The frequent localization of VHL-P in the nuclei of somatotroph adenomas, the least vascularized tumor type, suggests a possible inhibitory role of VHL-P in pituitary angiogenesis.

Endoscopic Pituitary Surgery: A Minimally Invasive Technique

The sublabial transseptal transsphenoidal approach using the operating microscope to provide illumination and magnification is the standard approach for the majority of pituitary adenomas in most institutions. This approach combines a sublabial incision with a transfixion incision, and often requires removal of the anterior nasal spine and dislocation or removal of the quadrilateral septal cartilage. We describe an endoscopic technique that is minimally invasive, requiring only a hemitransfixion incision, and preserving the anterior nasal spine. Often, it is not necessary to dislocate the septal cartilage from the maxillary crest. The surgery is performed using a 4 mm 0 degree telescope. Angled 30 degree and 70 degree telescopes are used to visualize the intrasphenoid anatomy, and may be introduced in the sellar cavity following tumor removal, to ensure complete extirpation. This minimally invasive technique has been successfully used in 80 patients with sellar lesions. The use of endoscopes offered not only the advantage of improved visualization, but also magnification and a panoramic perspective of the important anatomical relationships of the sella turcica. It also enabled more complete tumor removal with minimally invasive techniques.

Management of Individual Tumor Syndromes: Pituitary Neoplasia

The majority of pituitary adenomas associated with MEN 1 secrete prolactin or growth hormone. For both types, medical treatment is an acceptable option, particularly for prolactinomas. A significant number of patients with this syndrome will, however, require surgery because of ineffectiveness of medical therapy or compression or invasion of parasellar structures. This article discusses current strategies for the medical and surgical management of prolactinomas and of acromegaly, with special attention to the diagnostic and therapeutic pitfalls associated with MEN 1.

Ultrastructural markers in the pathologic diagnosis of pituitary adenomas.

The functional-morphologic classification of pituitary adenomas increased the number of distinguishable morphologic entities from 3 (acidophilic, basophilic, chromophobic) to 15. Identification of tumor types requires histology as well as immunohistochemistry and electron microscopy. Electron microscopy has a pivotal role in the recognition and separation of entities with overlapping immunohistochemical profiles. Electron microscopic diagnosis is facilitated considerably by structural markers present in the majority of adenoma types. Two groups of ultrastructural markers are discussed. Organelle markers are represented by specific morphology/arrangement of ubiquitous cytoplasmic constituents (rough endoplasmic reticulum, Golgi apparatus, mitochondria). Special markers are usually restricted to a particular pituitary cell type, its tumors, or both (filamentous aggregates, particular morphology of secretory granules, etc). Evaluation of general ultrastructural features and identification of structural markers permit conclusive diagnosis in the majority of pituitary adenomas. Cell derivation remains uncertain in many so-called clinically nonfunctioning adenomas with no or insufficient markers and poorly developed cytoplasmic organization associated with low endocrine activity.

Decreased tuberoinfundibular and pituitary dopamine and dihydroxyphenylacetic acid concentrations in rats with estrogen-induced pituitary tumors

The majority of pituitary adenomas are prolactin (PRL)-secreting, but it is still uncertain whether their pathogenesis results from a central nervous system (CNS) disturbance or autonomous lactotroph growth and function. We have measured dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) concentrations in rats bearing estradiol-induced PRL-secreting pituitary tumors. Female rats, injected at 3-week intervals with 2 mg estradiol valerate (EV), had increased plasma prolactin concentrations, up to 3 micrograms/ml, at 31 weeks. Inversely, there was a reduction of DA and DOPAC in the median eminence and arcuate nucleus as well as a decreased DOPAC/DA ratio in the arcuate nucleus. DA-containing nuclei in the other parts of the brain were not affected. Anterior pituitary weight increased while its DA concentration decreased during estradiol treatment. In the neurohypophysis, DA concentrations were unchanged while DOPAC and the ratio DOPAC/DA decreased following the estrogen treatment. Our data suggest that rats with primary estrogen-induced PRL-secreting tumors have a defect in the CNS-DA neurotransmission.

Ultrastructural features of human pituitary adenomas producing growth hormone, prolactin and thyrotrophin

The majority of pituitary adenomas are monohormonal and monomorphous, i.e. they produce only one hormone and are composed of one morphologic cell type. About 12-15% of pituitary adenomas are piurihormonal containing more than one hormone, either in one cell type (monomorphous) or 2 or more morphologic types (plurimorphous). Most piurihormonal adenomas produce growth hormone and prolactin. Other combinations are uncommon.We report here the ul trastructural features of 11 pituitary tumors which produced growth hormone (GH), prolactin (PRL) and thyrotrophin (TSH), as shown by immunohistochemistry. They were removed by surgery from 3 men and 8 women between 24 and 63 years of age. Eight tumors were associated with elevated blood GH levels and acromegaly. In 3 patients, blood prolactin levels were elevated. Hyperthyroidism was evident in 1 woman with elevated blood TSH levels.For fine structural studies, parts of tissue were fixed in 2.5% glutaraldehyde, postosmicated in 1% OsO4, dehydrated in graded ethanol, processed through propylene oxide and embedded in an Epon-Araldite mixture. Ultrathin sections were stained with uranyl acetate and lead citrate and investigated with a Philips 300 electron microscope.