Cytokeratin distribution and functional properties of growth hormone-producing pituitary adenomas

In addition to its structural function, cytokeratin may have other important roles within cells. We have reported that in growth hormone-producing adenomas (GH cell adenomas), two distinct types can be recognized by their cytokeratin distribution patterns (dot-like or perinuclear pattern) and that each type has different clinicopathological and endocrinological properties. To confirm these phenomena in a larger series and to clarify the significance of different cytokeratin distribution patterns, we studied cytokeratin localization in 70 GH cell adenomas from acromegalic patients. Type I adenomas ( 15) almost exclusively (>98%) composed of cells with a prominent, dot-like distribution; type 2 adenomas (36) comprised of cells with perinuclear cytokeratin; and type 3 adenomas (11) comprised of both cell types were separated. The remaining 8 did not exhibit a distinct distribution pattern. By electron microscopic immunocytochemistry for cytokeratin, dot-like distribution corresponded to fibrous bodies, whereas perinuclear distribution represented immune deposition in the perinuclear zone. Immunohistochemistry for GH, prolactin, β-thyrotropin, and α-subunit of glycoprotein hormones revealed a reduced expression of these hormones in type 1 adenomas, compared with types 2 and 3 adenomas. In normal pituitary glands, almost all GH cells showed a perinuclear cytokeratin distribution, and only a few GH cells exhibited a dot-like pattern. These findings suggest that a dot-like cytokeratin distribution in GH cells may be pathological (a change from physiological perinuclear distribution) and that adenomas with such a distribution may reduce endocrine activities as a result of unknown factors.     

Fluorescamine fluorescence detection of growth hormone-producing cells in human pituitary adenomas

Summary Formalin-fixed and paraplast-embedded tissue specimens of human pituitary, thyroid, and pancreas were investigated using fluorescamine fluorescence and immunohistochemical methods. Growth hormone-producing cells present in normal and neoplastic pituitary tissue exhibited fluorescamine fluorescence. The other tissues examined showed no fluorescamine binding.The authors are indebted to Mr. Klaas van der Ham for preparing the mierophotographs.     

Simultaneous production of the alpha-subunit of glycoprotein hormones and other hormones in pituitary adenomas

The immunohistological classification of 97 pituitary adenomas revealed in 34 cases alpha-subunit (a-su) positive cells in the tumor tissue. In 15 cases a-su was the only hormone found, in 11 cases the beta-subunits of the glycoprotein hormones could also be detected (10 cases with LH/FSH and 1 case with TSH). In 8 cases a-su was found simultaneously together with other hormones of the pituitary (ACTH and a-su in 1 case, GH and a-su in 4 cases, prolactin and a-su in 2 cases, prolactin, GH and a-su in 1 case). A-su could be demonstrated to be partly simultaneously produced together with these hormones in identical cells and secretory granules. Next to prolactin, the a-su was the second most frequently occurring hormone that could be detected immunohistologically in our material.     

Production of the alpha-subunit of glycoprotein hormones by pituitary adenomas

Positive immunoreactions with alpha-subunit antibodies were present in 43% of biopsy samples obtained from 147 subsequently operated pituitary adenomas representing all major endocrine types (57 endocrine inactive adenomas, 43 prolactinomas, 30 adenomas causing acromegaly, and 17 adenomas causing Cushing's disease or Nelson's syndrome). Marked variations of the incidence, however, were found among the individual endocrine groups. Positive reactions were present in 63% of endocrine inactive adenomas, 57% of adenomas causing acromegaly, 35% of ACTH-secreting adenomas, and 9% of prolactinomas. A positive alpha-subunit reaction was accompanied in a minority of cases only with positive glycoprotein hormone-beta-subunit reactions. There were 21 pure alpha-subunit adenomas in the group of endocrine inactive adenomas.     

Presence of neurophysins in the human pituitary corticotrophs, Cushing''s adenomas, and growth hormone-producing adenomas detected by immunohistochemical study.

Neurophysins have been recognized as the carrier proteins of vasopressin and oxytocin. The distribution of neurophysins is immunohistochemically confirmed in the hypothalamus, median eminence, and posterior lobe of the pituitary gland. The authors detected neurophysins in the human corticotrophs and pituitary adenomas with the use of the immunohistochemical method with antiserum to human neurophysins, which did not cross-react with adrenocorticotropic hormone (ACTH), beta-endorphin, and corticotropin-releasing factor. All of ten pituitary glands obtained by autopsy revealed the presence of neurophysin-positive cells in the anterior, intermediate, and the posterior lobes. The neurophysin-positive cells were similar to the corticotrophs in shape and distribution. Simultaneous staining for ACTH and neurophysins in the serial sections revealed that neurophysin-positive cells were also ACTH-positive. One hundred twenty-four cases of pituitary adenoma operated upon were investigated. All of 7 Cushing's adenomas were composed of neurophysin-positive cells. Six tumors with giantism showed sparsely distributed neurophysin-positive cells. No neurophysin-positive cells were observed in any other cases. This study is the first reported evidence of the presence of neurophysins in the human corticotrophs and pituitary adenomas.     

Expression of retinoblastoma protein in human growth hormone-secreting pituitary adenomas

The retinoblastoma gene (RB1) is a tumor-suppressor gene in chromosomal region 13q14.2. Its role in the pathogenesis of pituitary tumors has not been fully clarified. Some studies have shown that losses in this chromosomal region are related to aggressive tumor behavior, although the retinoblastoma protein (pRB) is still expressed. Conversely, lack of expression of pRB was observed in one fourth of GH-secreting pituitary adenomas (GH-tumors). In order to further study the expression of pRB in GH-tumors, we evaluated this protein in 49 tumors from patients with acromegaly (20 noninvasive, 25 invasive, and 4 with no information) and 8 normal pituitaries using immunohistochemistry (IHC). Nuclear staining for pRB ranged from 0 to 90% (median 40%) in the tumors and from 40 to 80% (median 58%) in normal pituitaries. In 10 tumors (20% of total) the adenomatous cells were negative (5 cases) or had very low labeling (5 cases) for pRB. Sixty three percent (31/49) of the tumors showed staining in 10–80% of the cells and in 16% (8/49) of the cases >80% of the adenomatous cells were positive for pRB. The expression of pRB was not different in invasive and noninvasive tumors. In conclusion, pRB is underexpressed in a subgroup of GH-tumors, and this may represent an early event in the pathogenesis of this tumor subtype.     

Expression of vascular endothelial growth factor in normal pituitary cells and pituitary adenomas producing adrenocorticotropic hormone

Vascular endothelial growth factor (VEGF) induces endothelial cell proliferation and an increase in capillary permeability. Because the anterior pituitary gland and pituitary adenomas are highly vascular, expression of VEGF was examined immunohistochemically. Some normal pituitary cells stained positively for VEGF, and restaining for ACTH, prolactin, TSH, LH, FSH, and S-100 protein after VEGF staining revealed that almost all cells staining positively for ACTH also stained for VEGF. Only adenomas staining positively for ACTH stained for VEGF. These results suggest that VEGF is produced by normal pituitary cells and adenomas producing ACTH.     

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.     

Fibrous bodies in growth hormone-secreting adenomas contain cytokeratin filaments

Fibrous bodies in growth hormone-secreting adenomas were studied by immunocytochemistry using an anti-cytokeratin antiserum. Fibrous bodies are a feature of acidophil and chromophobe adenomas and are usually associated with acromegaly. Ultrastructural examination revealed round juxtanuclear filamentous aggregates, composed of 8-nm filaments and other organelles. This study demonstrated that the intermediate filaments of fibrous bodies belong to the cytokeratin class. The etiology and significance of these filamentous aggregates remain obscure.     

The role of hypothalamic hormones in the pathogenesis of pituitary adenomas

There is evidence that hypothalamic hormones can regulate hormone secretion by pituitary adenomas. Hormone release by adenomas can be stimulated by hypothalamic releasing peptides; several hypothalamic inhibitory hormones or their analogues are used in the therapy of pituitary tumors to suppress hormone secretion and, in some cases, to reduce tumor size. A role for hypothalamic hormones in the development and growth of pituitary tumors has also been suggested by the association of pituitary adenomas with tumors producing hypothalamic hormones. In particular, tumors producing growth hormone-releasing hormone (GRH) or corticotropin-releasing hormone (CRH) have been associated with hyperplasia of their target adenohypophysial cells; a few have had pituitary neoplasms. Investigations have shown that some adenohypophysial cells respond to sustained stimulation by hypothalamic peptides with cell proliferation, however, it was not proven that the sustained stimulation resulted in the development of tumors. Recently, an animal model of disease was provided by mice transgenic for GRH. At 8 months of age, the mice developed pituitary mammosomatotroph hyperplasia; mice older than 12 months developed pituitary mammosomatotroph adenoma. It is suggested that continued hormonal stimulation plays a role in tumorigenesis, probably by promotion of cell replication.     

Free alpha subunit of the pituitary glycoprotein hormones. Measurement in serum and tissue of patients with pituitary tumors.

A solid-phase radioimmunoassay was developed that measures the free alpha subunits of pituitary glycoprotein hormones (alpha PGpHs) and has negligible cross-reactivity with the intact hormones (less than 0.014% for thyroid-stimulating hormone [TSH], less than 0.1% for human chorionic gonadotropin [hCG], 0.8% for luteinizing hormone [LH], and 2.0% for follicle-stimulating hormone [FSH]). The assay is standardized with the alpha subunit of hCG but also reacts well with the alpha subunits of the other glycoprotein hormones (84% for alpha TSH, 77% for alpha FSH, and 64% for alpha LH). Concentrations as low as 0.3 micrograms/L can be reliably measured, and the 97.5% reference range in 27 healthy adults, including postmenopausal females, is less than or equal to 1.2 micrograms/L. Elevated preoperative alpha PGpH concentrations were found in 45 (9.4%) of 479 sera from patients with pituitary adenoma and 3 (4.5%) of 66 patients with nonadenomatous sellar lesions. Postoperative alpha PGpH levels were lower in 30 of 39 adenoma patients and 2 of 3 nonadenoma patients. In five (1%) of the patients with pituitary adenomas, alpha PGpH was the only elevated serum hormone marker. Serum values of alpha PGpH correlate weakly with alpha subunit immunocytochemical staining--95% of those with negative staining have normal alpha PGpH values, but only 18% of those with positive staining have elevated alpha PGpH values.     

Plurihormonal pituitary adenomas: immunostaining of all pituitary hormones is mandatory for correct classification

AIMS: We studied the clinicopathological characteristics of plurihormonal pituitary adenomas. METHODS AND RESULTS: The study material included 167 plurihormonal adenomas, which consisted of 31% of the surgically removed pituitary adenomas that we collected during a 12-year period. The mean age of patients with plurihormonal adenoma was 45.7 years (range 13-75 years). There were 86 men and 81 women. All tumours were fully classified by immunohistochemical staining for seven pituitary hormones or subunits. Thirty immunohistochemical subtypes of plurihormonal adenomas were recognized. Hormonal symptoms were present in 70% of patients, while serum hormonal levels were increased in 89% of patients. Most patients had symptoms related to only one of the hormones and only 7% of patients had symptoms related to two hormones. The most common hormonal symptom was acromegaly (50%); symptoms related to hyperprolactinaemia ranked second (20%). Double immunostaining of all the possible combinations of the hormones was performed in 30 selected tumours, and they all showed mixtures of hormones in individual adenoma cells in any hormonal combinations studied. The latter finding supported the view that plurihormonal adenomas are monomorphous adenomas. CONCLUSIONS: Plurihormonal adenomas are common pituitary adenomas. Immunohistochemical staining of all pituitary hormones is mandatory for correct classification.     

Immunoelectron microscopic demonstration of glycoprotein subunits in the FSH producing pituitary adenomas

Immunoelectron microscopic observations disclosed the presence of FSH alpha, beta subunits in secretory granules and rough endoplasmic reticulum (RER). Golgi saccules were consistently negative. The presence of these subunits in secretory granules which were located in the vicinity of RER or perinuclear spaces (PNS) suggested the possible formation of secretory granules in RER or PNS. The tumor cells showed heterogeneity in size and immunoreactivity of the secretory granules but non-neoplastic cells showed uniformity in these aspects.     

Immunoelectron microscopy for growth hormone and prolactin in pituitary adenomas

Growth hormone (GH)- and prolactin (Prl)-producing pituitary adenomas were studied with immunoelectron microscopy using protein A-gold complex, and were compared with the normal pituitary gland. GH-producing cells were readily identifiable by numerous, uniformly dense, round secretory granules in both adenomas and normal pituitary gland. In contrast, Prl secretory granules in normal pituitary gland were much larger in size than the scarce, smaller, secretory granules of Prl-producing adenomas. Thus immunoelectron microscopic identification of Prl is more valuable for prolactinoma. With more specific antigens available as tumor markers, immunoelectron microscopy appears to be a powerful tool for tumor diagnosis.     

神经生长因子受体在垂体腺瘤中的表达

目的：探讨两种神经生长因子（ＮＧＦ）受体（ＴｒＫＡ和ｇｐ７５）在各类垂体腺瘤中的表达。方法：采用免疫细胞化学ＳＡＢＣ法,检测了４４例经病理证实的垂体腺瘤中两种ＮＧＦ受体的表达情况。结果：ＴｒＫＡ在垂体ＰＲＬ分沁腺瘤中的过度表达率６９．２％,而在其它类型垂体腺瘤中的过度表达率为１９．４％,两者比较差异有非常显著性（Ｐ〈０．００５）。ｇｐ７５在垂体ＰＲＬ分泌腺瘤中的过度表达率在４６．２％,而在其它类型