Morphologically unclassified GH-producing adenoma showing galactorrhea without acromegaly

A 24-year-old woman with a large pituitary adenoma had amenorrhea and galactorrhea, but no physical stigmata of acromegaly despite slightly elevated serum growth hormone (GH) and normal serum prolactin (PRL) levels. Subtotal removal of the tumor cured galactorrhea and resulted in normalization of serum GH concentration. The question is raised whether amenorrhea and galactorrhea were related to excessive GH production in this patient. Absence of acromegaly might have been due to the short duration of the disease. The tumor was a chromophobic, periodic acid-Schiff-negative adenoma. Immunocytochemistry and in situ hybridization revealed focal GH immunoreactivity and diffuse, weak signal for GH messenger RNA. By electron microscopy, the tumor showed no features of GH or PRL-producing adenomas. Two different cell types could be distinguished: the majority were similar to null cells, whereas a small number of cells resembled somatotrophs and lactotrophs, possessing many secretory granules and exhibiting exocytosis. On the basis of its ultrastructure, this tumor can be classified as an atypical acidophil cell line adenoma in which adenomatous null cells transformed to the differentiated cells capable of producing GH.     

Coexpression of galanin and adrenocorticotropic hormone in human pituitary and pituitary adenomas.

Galanin is a neuropeptide that regulates the secretion of several pituitary hormones, including prolactin (PRL) and growth hormone (GH). Galaninlike immunoreactivity (Gal-IR) and galanin mRNA in the rat anterior pituitary is cell lineage specific, with predominant expression in lactotrophs and somatotrophs. The authors examined the cellular distribution of human Gal-IR in seven normal postmortem pituitaries and 62 pituitary tumors by immunoperoxidase staining. In contrast to the rat, Gal-IR in human anterior pituitaries was present in corticotrophs scattered throughout the gland, but not in lactotrophs, somatotrophs, thyrotrophs, or gonadotrophs. Distinct Gal-IR also was present in hyperplastic and neoplastic corticotrophs in 19 of 22 patients with Cushing's disease. In noncorticotroph cell tumors, unequivocal Gal-IR was present in 5 of 11 GH-secreting tumors associated with clinical acromegaly, 9 of 18 nonfunctioning pituitary adenomas, and 2 of 14 prolactinomas. Of these galanin-positive tumors, four of the five GH-secreting adenomas, six of the nine nonfunctioning adenomas, and both of the prolactinomas also contained adrenocorticotropic hormone immunoreactivity (ACTH-IR). Immunostaining and in situ hybridization on adjacent sections using an 35S-labeled probe complementary to human galanin mRNA demonstrated predominant galanin expression in normal corticotrophs. Immunoelectron microscopy confirmed the presence of Gal-IR in pituitary cells characteristic of corticotrophs in both normal and neoplastic pituitaries. Thus, as in the rat, galanin gene expression in the human pituitary is cell-type specific. Unlike the rat, however, human galanin gene expression is restricted to the corticotroph lineage. Studies of tumors confirmed the observed coexpression of galanin and adrenocorticotropic hormone. The divergent cell type specificity of galanin production in human and rat pituitaries reflects different patterns of gene activation in these two species. In addition, these results suggest that galanin in the human pituitary may participate locally in the regulation of the hypothalamic-pituitary-adrenal axis.     

Human growth hormone and prolactin secreting pituitary adenomas analyzed by in situ hybridization

Acidophilic pituitary adenomas commonly produce growth hormone (GH) or prolactin (PRL), according to studies employing immunohistochemical and ultrastructural methods. To examine this question, in situ hybridization with oligonucleotide probes was done on routinely processed tissues received in the pathology laboratory to analyze for the presence of GH and PRL messenger RNA (mRNA) in 4 normal pituitaries, 10 prolactinomas, and 16 GH-secreting adenomas. Most acidophilic cells in normal pituitaries expressed either GH or PRL hormone and the respective mRNAs, but GH mRNA and PRL hormone were also detected in some of the same cells. Patients with a clinical diagnosis of prolactinoma had cells with only PRL mRNA in their tumors, while most (14 of 16) patients with a clinical diagnosis of acromegaly or gigantism had both GH and PRL mRNAs in their tumors. The GH adenomas varied in these studies. In situ hybridization was helpful in characterizing the adenoma from a patient with acromegaly who had immunoreactive PRL, but no immunoreactive GH in the resected tumor; in situ hybridization analysis revealed mRNAs for both GH and PRL in the same tumor cells. Our findings indicate that pituitary adenomas from patients with acromegaly commonly express PRL mRNA. It is concluded that in situ hybridization provides new information about the clinical biology and the histopathologic classification of pituitary adenomas.     

Ultrastructural and Immunoelectron Microscopic Study of Three Unusual Plurihormonal Pituitary Adenomas

Momomorphous pituitary adenomas expressing several hormones by immunocytochemistry are common, whereas adenomas displaying multiple immunoreactivities and consisting of more than one morphologic cell types are rare. Three such unusual pituitary adenomas, surgically removed from two patients with acromegaly and one patient with hyperprolactinemia, were investigated by histology, immunocytochemistry, transmission electron microscopy, as well as immunoelectron microscopy using double immunogold labeling. Immunocytochemistry revealed variable degrees of immunoreactivities for growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (beta-TSH), and alpha-subunit of glycoprotein hormones in all three tumors. The three adenomas consisted of phenotypically diverse cell populations as documented by transmission electron microscopy. In addition to monohormonal GH cells, immunoelectron microscopy demonstrated numerous cells colocalizing GH and PRL or GH and beta-TSH, and rarely PRL and beta-TSH in tumors of acromegalics. The adenoma causing hyperprolactinemia consisted chiefly of mammosomatotrophs colocalizing PRL and GH, whereas beta-TSH labeling was scant. The three tumors in the study were selected from a cluster of five plurimorphous plurihormonal adenomas received from the same locale where they accounted for an unprecedented 21% of adenomas producing GH and/or PRL. The enhanced susceptibility to develop plurimorphous adenomas of the acidophil cell line may have a genetic basis in the stable population the patients came from.     

Somatotropic adenomas without acromegaly.

Seventeen somatotropic adenomas removed from patients without acromegaly were studied. Thirteen of them presented as a prolactinoma with amenorrhea and/or galactorrhea and elevated serum PRL levels. According to basal serum GH levels, the patients were divided into two groups, namely Group I: GH slightly elevated (n = 4) and group II: GH less than or equal to 5 micrograms/l (n = 13). The tumoral GH secretion was proved by immunocytochemistry in all cases and by intratumoral RIA, in vitro study and/or in situ hybridization in five of them. Pathological, clinical and biochemical relationships suggested two anatomoclinical aspects. In group I, the tumors were small, well-differentiated somatotropic adenomas with clinically silent GH hypersecretion. It is probably an early stage of the disease. In group II, the tumors were large with normal GH serum levels. They were poorly differentiated and secreted very low amounts of GH. In nine of them, PRL and/or PRL mRNA expression were also detected. These tumors do not secrete enough GH to increase serum levels and cause acromegaly. The somatotropic adenomas without acromegaly correspond to two anatomoclinical aspects of the disease.     

Reversible transdifferentiation: interconversion of somatotrophs and lactotrophs in pituitary hyperplasia.

Previous studies conclusively demonstrated transformation of somatotrophs into bihormonal mammosomatotrophs in gestational lactotroph hyperplasia during pregnancy. Similar transdifferentiation of somatotrophs into thyrotrophs through bihormonal intermediate thryrosomatotrophs was documented during thyrotroph hyperplasia in both rodent and human pituitaries in hypothyroidism. The cessation of the stimulation resulted in reversal of the process in both conditions. The conversion of lactotrophs into somatotrophs was suggested but not documented previously in the human gland. The present study was undertaken to investigate cases of somatotroph hyperplasia by transmission electron microscopy, immunoelectron microscopy using double immunogold labeling for growth hormone and prolactin, as well as combined immunocytochemistry and in situ hybridization. Adenohypophysial tissue was removed from a 38-year-old man and a 29-year-old woman with long-standing acromegaly due to ectopic overproduction of growth hormone-releasing hormone (GRH) by bronchial carcinoid tumors. For comparison, two pituitary biopsies were studied: one from a 38-year old woman with idiopathic lactotroph hyperplasia and one from a 14-year-old boy with secondary lactotroph hyperplasia due to a suprasellar craniopharyngioma. In the patients with somatotroph hyperplasia, the prevailing cell type was the hyperplastic somatotroph joined by mammosomatotroph deriving from lactotrophs, whereas monohormonal lactotrophs were rare. The predominance of mammosomatotrophs and active lactotrophs was documented in the patient with idiopathic lactotroph hyperplasia, whereas the case of the patient with secondary lactotroph hyperplasia was characterized by monohormonal lactotrophs and somatotrophs, but mammosomatotrophs were rare. That finding in the pituitary of the boy suggests that participation of mammosomatotrophs in lactotroph hyperplasia is not unconditional Our findings conclusively demonstrate conversion of lactotrophs into mammosomatotrophs during somatotroph hyperplasia, providing further evidence for the potential of reversible transdifferentiation between somatotrophs and lactotrophs in response to functional demand.     

Electron microscopic studies of human pituitary tumors. II. Acidophilic adenomas

Nine cases of acidophilic adenoma associated with acromegaly were studied by electron microscopy. The tumor parenchyma contained numerous cells identifiable as somatotrophs, many of which appeared “normalt” and apparently engaged in protein synthesis. In about half of the specimens, there were variations in the electron-opaque characteristics of the parenchymal cells, most frequently affecting somatotrophs. Characteristic of some somatotrophs was a marked electron-opacity of the cytoplasmic matrix and nuclear materials, irregular cell contours, hypertrophied cytomembrane systems frequently containing proteinaceous material, and considerable amounts of secretory granules. Disruptions in plasma membranes were apparent throughout the parenchyma, particularly at the parenchymal-pericapillary interface. This resulted in the release of large numbers of secretory granules and cytoplasmic fragments to pericapillary or extracellular spaces. Small groupings of the disrupted cells often were characterized by scant secretory granules, an electron-lucent cytoplasmic matrix, and were considered the counterpart of giant multinucleate chromophobes observed with the light microscope. Follicular cells were observed rarely, but when present contained an abundance of fine cytoplasmic filaments and closely resembled follicular cells described in ACTH-secreting tumors.     

Growth hormone-releasing hormone receptor mRNA in acromegalic pituitary tumors.

The growth hormone (GH)-releasing hormone receptor (GHRH-R) has been recently cloned and found to be a member of a new family of seven transmembrane receptors that includes secretin, vasoactive intestinal peptide, calcitonin, and corticotropin-releasing factor. GHRH-R mRNA has been demonstrated by Northern blot analyses to be present specifically in the anterior pituitary gland. To determine the precise cellular localization of this receptor in normal anterior pituitary and pituitary adenomas, GHRH-R mRNA was analyzed in 2 normal human pituitary glands and 16 human pituitary adenomas using in situ hybridization. GHRH-R was specifically localized in somatotroph cells in the normal pituitary. In the adenomas, all GH-producing adenomas originating from acromegalic patients demonstrated up-regulation of GHRH-R mRNA when compared with levels in the normal pituitary. Only one of five clinically nonfunctioning adenomas, a gonadotroph luteinizing hormone/follicle-stimulating hormone-positive adenoma, exhibited up-regulation of this receptor message. Adrenocorticotrophic hormone-secreting and prolactin-secreting adenomas did not express GHRH-R message. In summary, GHRH-R is specifically expressed in somatotrophs and GH-producing adenomas, suggesting that GHRH-R may influence GH release in adenomas similar to this receptor's actions in the normal somatotrophs and may be involved in the growth of GH-secreting adenomas.     

An Atypical Acidophil Cell Line Tumor Showing Focal Differentiation Toward Both Growth Hormone and Prolactin Cells

We report a case of giant pituitary adenoma in a child. Computerized tomography (CT) scan revealed a suprasellar extension tumor mass with hydrocephalus. There was no clinical evidence of acromegaly, gigantism, and other hormonal symptoms. Endocrinologic studies showed within normal value of serum growth hormone (GH: 4.2 ng/mL) and slightly increased levels of prolactin (PRL: 78 ng/mL) and other pituitary hormone values were within normal range. On suppression test by bromocryptin, both GH and PRL levels were reduced. Histopathological findings revealed that the tumor consisted of predominantly chromophobic and partly eosinophilic adenoma cells. Immunohistochemical staining detected GH and PRL in a small number of distinctly different adenoma cells, respectively. Nonradioactivein situ hybridization (ISH) also showed GH and PRL mRNA expression in identical immunopositive cells. Electron microscopy (EM) demonstrated adenoma cells with moderate or small numbers of two types of dense granules and without fibrous body which are characteristic of sparsely granulated GH-cell adenomas. The adenoma does not fit into any classification but may be an atypical acidophil cell line tumor showing focal differentiation toward both GH and PRL cells.     

In situ hybridization for different mRNA in GH-secreting and in inactive pituitary adenomas

In a series of 40 pituitary adenomas in acromegaly all tumors showed mRNA for GH by in situ hybridization (ISH). The signals were mostly very strong and found in more than 80% of adenoma cells by using frozen sections. In paraffin sections the number of positive cells and the intensity of signals are lower. Prolactin mRNA was found in 87% of adenomas. In 27% more than 80% of cells were marked. beta-HCGmRNA (with 90% hormology for LH-mRNA) was demonstrable in very sparse cells of 25% of adenomas. Comparing ISH with immunohistology (IH) we found a correlation between signals and hormone content in 100% of adenomas for GH, in 60% for Prolactin and in 10% for Gonadotropins. In 18% Prolactin mRNA but not the hormone was demonstrable and in 5% Prolactin was immunostained but no hybridization signals were detected. In a series of 40 clinically inactive adenomas sparse cells of three tumors expressed GHmRNA and two of these contained also the hormone, whereas in one adenoma GH but not GHmRNA was demonstrable. Prolactin mRNA was found in 8 adenomas. 7 of these also contained the hormone. In two cases Prolactin but not Prolactin mRNA was present. Beta-HCG(LH)mRNA and the respective hormones were shown in very sparse cells of 6 adenomas, whereas only beta-HCG(LH)-mRNA was found in 8 cases. The significance of the findings is discussed.     

Pancreastatin secretion by pituitary adenomas and regulation of chromogranin B mRNA expression.

Pancreastatin, a carboxyl-terminal amidated peptide derived from chromogranin (Cg)A, inhibits secretion of insulin and parathyroid hormone. Our recent studies found significant amounts of immunoreactive pancreastatin in all pituitary adenomas except prolactin adenomas. To analyze the effects of pancreastatin on pituitary cell function, 17 cultured pituitary adenomas were examined for immunoreactive pancreastatin and pancreastatin secretion by the tumors. The effects of pancreastatin on pituitary hormone secretion and on pituitary hormone (follicle-stimulating hormone and prolactin), CgA, and CgB mRNA levels were also examined. Immunoreactive pancreastatin and CgA were present diffusely in gonadotroph and null cell adenomas, but only a few prolactin adenoma cells expressed pancreastatin or CgA. When cells were treated with hypothalamic peptides, gonadotroph adenomas were the only group that released increased amounts of pancreastatin in response to gonadotropin-releasing hormone (10(-7) mol/L). Pancreastatin (10(-7) mol/L) treatment did not stimulate pituitary hormone secretion significantly. In situ hybridization analyses showed that gonadotropin-releasing hormone and pancreastatin treatment led to significant increases in CgB and follicle-stimulating hormone mRNAs in gonadotroph adenomas, whereas CgA mRNA levels did not change significantly. These results show that there is a differential distribution of pancreastatin secretion in pituitary adenomas and that the hypothalamic hormone gonadotropin-releasing hormone and the CgA-derived peptide pancreastatin can regulate CgB mRNA in gonadotroph adenomas, suggesting an autocrine effect of pancreastatin on pituitary tumor function.     

The TSH secretion in the human pituitary adenomas

TSH secretion by a pituitary tumor is very rare (2%) and it is often associated with another hormone: GH or PRL essentially. We present here nine tumors in which the TSH secretion was proved by immunocytochemistry (ICC) and by RIA in the tumor extracts, in the serum and in the culture medium. Four tumors secreted TSH only. Five tumors secreted TSH and GH predominantly. In 3 of them traces of other hormones (PRL and FSH) were also detected. The "pure" TSH adenomas were monomorphous with typical ultrastructural and immunocytochemical features. Plurihormonal TSH adenomas were bimorphous with different cells secreting GH and TSH or monomorphous with one type of cell which secreted TSH or GH or both TSH and GH. In a majority of the cases, the tumoral TSH secretion induced hyperthyroidism but in 2 patients with TSH adenoma there was euthyroidism and in another with TSH-GH adenoma there was no sign of acromegaly and GH serum levels were normal.     

Pathology of growth hormone-producing tumors of the human pituitary

This paper reviews the morphologic features of growth hormone-producing tumors of the human pituitary. These tumors are associated with elevated blood growth hormone levels and acromegaly or gigantism and can be classified into the following morphologically distinct entities by the combined application of histology, immunocytology, and electron microscopy: densely granulated growth hormone cell adenoma; sparsely granulated growth hormone cell adenoma; mixed growth hormone cell- prolactin cell-adenoma; acidophil stem cell adenoma; mammosomatotroph cell adenoma; growth hormone cell carcinoma; plurihormonal adenoma with growth hormone production.     

Mutations in the alpha subunit of the stimulatory regulatory protein of adenylyl cyclase (Gs) in human GH-secreting pituitary adenomas. Biochemical, clinical, and morphological aspects

Very recently a subset of human GH-secreting pituitary adenomas carrying a somatic mutation in the alpha subunit of the stimulatory regulatory protein of adenylyl cyclase (Gs) was identified. In all these tumors (Group 2; about 30% of all the GH secreting tumors studied) the alpha s cDNAs contained mutations; in 8 tumors mutations replaced Arginine 201 with either Cystein or Histidine while in the remaining tumors Glutamine 227 was replaced by either Arginine or Leucine. No mutations were observed in the remaining adenomas (Group 1). The two mutations caused a constitutive activation of adenylyl cyclase and a turn on of cAMP synthesis by inhibiting GTPase activity. The transformed phenotype was reflected in adenomatous cells with high rate of cAMP production and in vitro GH secretion. No difference in age, sex, clinical features, duration of the disease and cure rate were observed between the patients without (Group 1) or with alpha s mutation (Group 2), while higher serum GH levels and smaller tumor size were present in Group 2 patients. Moreover, hypersecretory activity in Group 2 tumors was also apparent at electron microscopy; cells of Group 2 tumors were densely granulated and showed prominent rough endoplasmic reticulum and Golgi complex. With respect to Group 1, Group 2 patients were less responsive to GH-releasing hormone (GHRH), while they were more sensitive to somastostatin. The former finding is in agreement with the hypothesis that the oncogenic proteins mimic the effects of extracellular growth factors, so removing the requirement for GHRH; the latter might explain the low rate of tumor growth as due to the counteracting role of endogenous inhibitory factors.     

Pituitary adenomas producing growth hormone, prolactin, and one or more glycoprotein hormones: a histologic, immunohistochemical, and ultrastructural study of four surgically removed tumors

The morphologic features of four pituitary adenomas, removed from 2 men and 2 women between 31 and 62 years of age, are reported. The tumors contained growth hormone (GH), prolactin (PRL), and one or more glycoprotein hormones--usually thyrotropin (TSH). Three tumors were associated with acromegaly and one with hyperprolactinemia. Hyperthyroidism was not evident in any of the patients. In the tumors of acromegalic subjects, GH-containing cells were the most numerous, whereas PRL cells were dominant in the adenoma accompanied by hyperprolactinemia. Electron microscopy revealed plurimorphous tumors comprised of various proportions of morphologically different cell types: densely granulated GH cells, TSH-like cells, and the less common mammosomatotrophs and PRL cells. It is suggested that pituitary adenomas producing GH, PRL, and glycoprotein hormones derive from the same precursor; their immunocytochemical profile, fine structural appearance, and endocrine function may depend on the degree and direction of the cellular differentiation.     

Pituitary Adenomas Producing Growth Hormone, Prolactin, and One or More Glycoprotein Hormones: A Histologic, Immunohistochemical, and Ultrastructural Study of Four Surgically Removed Tumors

The morphologic features of four pituitary adenomas, removed from 2 men and 2 women between 31 and 62 years of age, are reported. The tumors contained growth hormone (GH), prolactin (PRL), and one or more glycoprotein hormones-usually thyrotropin (TSH). Three tumors were associated with acromegaly and one with hyperprolactinemia. Hyperthyroidism was not evident in any of the patients. In the tumors of acromegalic subjects, GH-containing cells were the most numerous, whereas PRL cells were dominant in the adenoma accompanied by hyperprolactinemia. Electron microscopy revealed plurimorphous tumors comprised of various proportions of morphologically different cell types: densely granulated GH cells, TSH-like cells, and the less common mammosomatotrophs and PRL cells. It is suggested that pituitary adenomas producing GH, PRL, and glycoprotein hormones derive from the same precursor; their immunocytochemical profile, fine structural appearance, and endocrine function may depend on the degree and direction of the cellular differentiation.     

Pituitary Adenomas Producing Growth Hormone,Prolactin, and One or More Glycoprotein Hormones: A Histologic,Immunohistochemical, and Ultrastructural Study of Four Surgically Removed Tumors

The morphologic features of four pituitary adenomas, removed from 2 men and 2 women between 31 and 62 years of age, are reported. The tumors contained growth hormone (GH), prolactin (PRL), and one or more glycoprotein hormones–usually thyrotropin (TSH). Three tumors were associated with acromegaly and one with hyperprolactinemia. Hyperthyroidism was not evident in any of the patients. In the tumors of acromegalic subjects, GH-containing cells were the most numerous, whereas PRL cells were dominant in the adenoma accompanied by hyperprolactinemia. Electron microscopy revealed plurimorphous tumors comprised of various proportions of morphologically different cell types: densely granulated GH cells, TSH-like cells, and the less common mammosomatotrophs and PRL cells. It is suggested that pituitary adenomas producing GH, PRL, and glycoprotein hormones derive from the same precursor; their immunocytochemical profile, fine structural appearance, and endocrine function may depend on the degree and direction of the cellular differentiation.     

Pathology of growth hormone excess

This paper briefly reviews the pathology of growth hormone excess. Prolonged oversecretion of growth hormone is associated with elevated serum growth hormone as well as somatomedian C levels and the clinical signs and symptoms of acromegaly or gigantism. Morphologic studies, including immunohistochemistry and electron microscopy, revealed that several distinct morphologic lesions can be present in the pituitary gland of patients with acromegaly or gigantism. Although substantial progress has been achieved during the last two decades, more work is required to correlate the morphologic features of adenoma cells with their biologic behavior. We feel that the future can be viewed with optimism and further exciting results can be expected by the interaction of pathologists, clinical endocrinologists and basic scientists.     

Recognition of gonadotroph adenomas in women

BACKGROUND. Pituitary adenomas that arise from the gonadotroph cells are being recognized with increasing frequency in men, but they are still rarely recognized in women. This rarity could be the result of an actual difference in occurrence or of greater difficulty in recognition. The tumors are usually recognized in men more than 50 years old, but elevated serum gonadotropin levels in women of that age could be produced by normal gonadotroph cells. METHODS. Because the stimulation of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and the beta subunit of LH (LH beta) by thyrotropin-releasing hormone (TRH) is a characteristic of gonadotroph adenomas in men, we administered TRH to 16 women with apparently nonsecreting pituitary macroadenomas and measured serum FSH, LH, LH beta, and the glycoprotein hormone alpha subunit every 15 minutes for 90 minutes before and 90 minutes after. The results were compared with the responses in 16 healthy women matched for age and in 10 women with macroadenomas secreting prolactin, growth hormone, or corticotropin. The tumors from 12 of the women with nonsecreting adenomas were cultured, and the secretion of FSH, LH, and LH beta in culture was determined. RESULTS. Eleven of the 16 women with apparently nonsecreting adenomas had significant increases in serum LH beta in response to TRH, 3 had FSH responses, and 4 had LH responses. None of the 16 healthy women and none of the 10 women with secreting macroadenomas had LH beta, FSH, or LH responses to TRH. Ten of the 12 adenomas that were cultured secreted readily detectable amounts of FSH, LH, and LH beta, and their secretion in vitro correlated with the patients' responses to TRH in vivo. CONCLUSIONS. Most apparently nonsecreting pituitary macroadenomas in women arise from gonadotroph cells. The majority of these can be recognized, even in postmenopausal women, by the serum LH beta responses to TRH, and some can be recognized by the responses of serum FSH and LH.