Pure alpha-secreting pituitary adenomas

The Role of Human Chorionic Gonadotropin as Tumor Marker: Biochemical and Clinical Aspects

Tumor markers are biological substances that are produced/released mainly by malignant tumor cells, enter the circulation in detectable amounts and are potential indicators of the presence of a tumor. The most useful biochemical markers are the tumor-specific molecules, i.e., receptors, enzymes, hormones, growth factors or biological response modifiers that are specifically produced by tumor cells and not, or minimally, by the normal counterpart (Richard et al. Principles and practice of gynecologic oncology. Wolters Kluwer Health, Philadelphia, 2009). Based on their specificity and sensitivity in each malignancy, biomarkers are used for screening, diagnosis, disease monitoring and therapeutic response assessment in clinical management of cancer patients.This chapter is focused on human chorionic gonadotropin (hCG), a hormone with a variety of functions and widely used as a tumor biomarker in selected tumors. Indeed, hCG is expressed by both trophoblastic and non-trophoblastic human malignancies and plays a role in cell transformation, angiogenesis, metastatization, and immune escape, all process central to cancer progression. Of note, hCG testing is crucial for the clinical management of placental trophoblastic malignancies and germ cell tumors of the testis and the ovary. Furthermore, the production of hCG by tumor cells is accompanied by varying degrees of release of the free subunits into the circulation, and this is relevant for the management of cancer patients (Triozzi PL, Stevens VC, Oncol Rep 6(1):7-17, 1999).The name chorionic gonadotropin was conceived: chorion derives from the latin chordate meaning afterbirth, gonadotropin indicates that the hormone is a gonadotropic molecule, acting on the ovaries and promoting steroid production (Cole LA, Int J Endocrinol Metab 9(2):335-352, 2011). The function, the mechanism of action and the interaction between hCG and its receptor continue to be the subject of intensive investigation, even though many issues about hCG have been well documented (Tegoni M et al., J Mol Biol 289(5):1375-1385, 1999).

Identification of growth arrest and DNA-damage-inducible gene beta (GADD45beta) as a novel tumor suppressor in pituitary gonadotrope tumors

Gonadotrope and null cell pituitary tumors cause significant morbidity, often presenting with signs of hypogonadism together with visual disturbances due to mass effects. Surgery and radiation are the only therapeutic options to date. To identify dysregulated genes and pathways that may play a role in tumorigenesis and/or progression, molecular profiling was performed on 14 gonadotrope tumors, with nine normal human pituitaries obtained at autopsy serving as controls. Bioinformatic analysis identified putative downstream effectors of tumor protein 53 (p53) that were consistently repressed in gonadotrope pituitary tumors, including RPRM, P21, and PMAIP1, with concomitant inhibition of the upstream p53 regulator, PLAGL1(Zac1). Further analysis of the growth arrest and DNA damage-inducible (GADD45) family revealed no change in the p53 target, GADD45α, but identified repression of GADD45β in pituitary tumors in addition to the previously reported inhibition of GADD45γ. Overexpression of GADD45β in LβT2 mouse gonadotrope cells blocked tumor cell proliferation and increased rates of apoptosis in response to growth factor withdrawal. Stable gonadotrope cell transfectants expressing increased GADD45β showed decreased colony formation in soft agar, confirming its normal role as a tumor suppressor. Unlike previous studies of GADD45γ in pituitary tumors and α and β in other tumors, bisulfite sequencing showed no evidence of hypermethylation of the GADD45β promoter in human pituitary tumor samples to explain the repression of its expression. Thus, GADD45β is a novel pituitary tumor suppressor whose reexpression blocks proliferation, survival, and tumorigenesis. Together these studies identify new targets and mechanisms to explore in pituitary tumor initiation and progression.

Bone morphogenetic protein and retinoic acid-inducible neural specific protein-3 is expressed in gonadotrope cell pituitary adenomas and induces proliferation, migration, and invasion

Pituitary tumors are common intracranial neoplasms that often result in endocrine dysfunction due to hormone overproduction or deficiencies from mass effects. Gonadotrope cell or gonadotropinomas are tumors that produce LH and/or FSH and represent 40% of macroadenomas. Little is known about their underlying pathogenic mechanisms. We compared expression profiles of 10 gonadotropinomas with nine normal pituitaries by cDNA array and identified bone morphogenetic protein- and retinoic acid-inducible neural-specific protein-3 (BRINP3) as overexpressed in tumors, compared with normals. BRINP3 is a novel, normally brain restricted protein of unknown function. BRINP3 mRNA was expressed selectively in gonadotropinomas. Subcellular localization studies showed that BRINP3 was targeted to the mitochondria, but BRINP3 overexpression was unable to protect pituitary cells against programmed cell death induced by growth factor withdrawal. However, BRINP3 overexpression in pituitary gonadotrope cells promoted proliferation, migration, and invasion. A BRINP3 antibody was raised that demonstrated clustered expression of BRINP3 protein in gonadotropinomas and not in normal human pituitary samples. Thus, BRINP3 is a mitochondrially localized protein that is selectively up-regulated in human gonadotropinomas. Its actions to increase proliferation, migration, and invasion suggest it may play an important role in pituitary tumorigenesis.

Human chorionic gonadotropin in cancer

Human chorionic gonadotropin (hCG) is mainly used for detection and monitoring of pregnancy and pregnancy-related disorders but it is also an extremely sensitive and specific marker for trophoblastic tumors of placental and germ cell origin. Thus treatment of relapsing choriocarcinomas and testicular germ cell tumors is often initiated on the basis of rising hCG levels even in the absence of clinical or histological evidence of a relapse. While these tumors mostly produce the intact heterodimeric hormone consisting of an alpha (hCGalpha), and a beta subunit (hCGbeta), many nontrophoblastic tumors produce only hCGbeta This is usually a sign of aggressive disease and elevated serum levels of hCGbeta are strongly associated with poor prognosis. Elevated serum levels are observed in 45-60% of patients with biliary and pancreatic cancer and in 10-30% of most other cancers. Methods that detect hCG and hCGbeta together are mainly used for measurement of hCG-like immunoreactivity in serum. However, the reference range for hCG is 5-8 fold higher than that for hCGbeta and thus moderately elevated levels can be identified only with a specific and sensitive hCGbeta assay.

Gonadotropin-secreting pituitary tumor associated with hypersecretion of testosterone and hypogonadism after hypophysectomy

OBJECTIVE

To review gonadotropin-secreting pituitary tumors and report the rare case of one of these tumors that caused high serum testosterone concentrations, followed by hypogonadism after hypophysectomy.

METHODS

A case report is presented of a 61-year-old man who had decreased vision in his left eye, found by computed tomography of the sella to be attributable to a soft tissue pituitary mass with upward extension that caused elevation and deviation of the optic chiasm. Endocrine and pathologic evaluations are presented, and the treatment and follow-up course are discussed.

RESULTS

Endocrine evaluation revealed a serum follicle-stimulating hormone (FSH) of 72.48 mIU/mL, luteinizing hormone (LH) of 31.65 mIU/mL, prolactin of 26.42 ng/mL, and total testosterone of 15.24 ng/mL (all values higher than the normal ranges). A soft tissue mass (3.2 by 2.5 by 1.2 cm) with negative immunocytochemical staining for prolactin and growth hormone but positive staining for synaptophysin, FSH, and LH was removed. One month postoperatively, the patient's chief complaints were a decrease in penile size and erectile dysfunction. Endocrine evaluation revealed a decreased LH of <0.3 mIU/mL, total testosterone of <0.2 ng/mL, and FSH of 4.3 mIU/mL. Three months later with testosterone replacement therapy, testosterone levels normalized, LH was <0.3 mIU/mL, and FSH was 3.9 mIU/mL. Thyroid function and adrenal function were normal before and after surgical intervention.

CONCLUSION

This rare case indicates that gonadotropin tumors can produce a functional LH that can increase serum testosterone levels.

Medical therapy of gonadotropin-producing and nonfunctioning pituitary adenomas

Clinically nonfunctioning pituitary adenomas are one of the most common types of pituitary tumors. Unless they present with symptoms related to local mass effect, most tumors are detected incidentally when imaging studies are performed for other reasons. Although clinically nonfunctioning, most of these tumors have evidence, in vitro, of gonadotropin hormone or glycoprotein subunit production. The gonadotropins or their monomer submits rarely cause clinically identifiable effects. When these tumors present as macroadenomas, often with associated mass effect and hypopituitarism, primary therapy is neurosurgery. The role for medical therapy will be reviewed here.

Serum alpha-subunit levels in patients with pituitary adenomas

OBJECTIVE

We investigated preoperative and postoperative serum alpha-subunit levels and the alpha-subunit response to TRH in patients with various types of pituitary tumour and correlated the data with histological findings in order to clarify the significance of alpha-subunit measurement in pituitary adenomas.

PATIENTS

We examined 59 patients with pituitary tumours (22 with GH cell adenomas, 30 with clinically nonfunctioning adenomas and seven with other tumours) treated at Toranomon Hospital between 1996 and 1998.

RESULTS

The basal alpha-subunit level was supranormal in six out of 22 (27%) patients with a GH cell adenoma and in nine out of 30 (30%) patients with a nonfunctioning adenoma. A paradoxical alpha-subunit response to TRH was found in seven out of 22 (32%) patients with a GH cell adenoma. These seven patients also showed a paradoxical GH response to TRH administration. In addition, paradoxical response to TRH was found in eight out of 30 (27%) patients with a clinically nonfunctioning adenoma. In contrast, patients with other types of pituitary tumour showed neither a supranormal alpha-subunit level nor a paradoxical response to TRH. The supranormal alpha-subunit level and the abnormal response to TRH were normalized in both GH cell adenoma and nonfunctioning adenoma patients after successful surgery. Immunohistochemical studies showed alpha-subunit positive cells in 51% of GH cell adenomas or nonfunctioning adenomas and there was a good concordance with the serum alpha-subunit levels in both GH cell adenoma and nonfunctioning adenoma patients.

CONCLUSIONS

These findings suggest that supranormal serum alpha-subunit levels are mainly due to hypersecretion by the tumour itself, while the paradoxical alpha-subunit response to TRH is an associated phenomenon in patients with a GH cell adenoma or nonfunctioning adenoma. The alpha-subunit level and the response to TRH may be useful indicators for assessing the operative outcome, especially in nonfunctioning adenoma patients who have no other definite endocrine markers.

Prolactin: structure, function, and regulation of secretion

Prolactin is a protein hormone of the anterior pituitary gland that was originally named for its ability to promote lactation in response to the suckling stimulus of hungry young mammals. We now know that prolactin is not as simple as originally described. Indeed, chemically, prolactin appears in a multiplicity of posttranslational forms ranging from size variants to chemical modifications such as phosphorylation or glycosylation. It is not only synthesized in the pituitary gland, as originally described, but also within the central nervous system, the immune system, the uterus and its associated tissues of conception, and even the mammary gland itself. Moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in homeostasis. Prolactin-releasing stimuli not only include the nursing stimulus, but light, audition, olfaction, and stress can serve a stimulatory role. Finally, although it is well known that dopamine of hypothalamic origin provides inhibitory control over the secretion of prolactin, other factors within the brain, pituitary gland, and peripheral organs have been shown to inhibit or stimulate prolactin secretion as well. It is the purpose of this review to provide a comprehensive survey of our current understanding of prolactin's function and its regulation and to expose some of the controversies still existing.

Immunohistochemical evaluation of the post-translational processing of chromogranin A in human pituitary adenomas

Chromogranin A (CgA), pancreastatin (PST), intervening-peptide (IP) and WE-14 antisera were employed to investigate the proteolysis of CgA in 50 pituitary adenomas. All non-functioning (NF) pituitary tumours (n = 28) exhibited CgA immunoreactivity. PST, IP and WE-14 immunostaining was observed in 85%, 89% and 67%, respectively. CgA, PST and IP immunostaining were comparable in the majority of NF tumours, while less intense WE-14 immunoreactivity was detected in a subpopulation of NF tumour cells. Approximately half of the functioning pituitary tumours expressed CgA immunoreactivity. Six of nine ACTH-secreting tumours displayed CgA and IP immunostaining; four of these tumours displayed PST immunoreactivity. WE-14 immunoreactivity was detected in one corticotroph tumour. Three of six growth hormone (GH) secreting tumours displayed CgA immunostaining, two exhibited PST and IP, and one exhibited WE-14 immunoreactivity. Clusters of WE-14 immunopositive cells were detected in one GH tumour. One of seven prolactinomas exhibited weak CgA immunostaining, while weak IP and WE-14 immunostaining was detected in an additional tumour. No PST immunostaining was detected in prolactinomas. Therefore CgA is a valuable marker of NF pituitary tumours, however it is a more sporadic marker of functioning adenomas. In general, the cellular pattern and intensities of CgA, PST and IP immunoreactivity were comparable in the majority of pituitary adenomas. In contrast, WE-14 immunostaining was observed in a subpopulation of tumour cells. The pathophysiological significance of the proteolysis of CgA to generate bioactive peptides in both NF and functioning pituitary adenomas remains to be established.

Medical therapy for gonadotroph and thyrotroph tumors

Gonadotroph adenomas, a common type of pituitary tumor, are not associated with syndromes of hormonal hypersecretion and thus present as pituitary macroadenomas with mass effects, or as incidentally discovered pituitary masses. When indicated, primary therapy is neurosurgery, but there may be a limited role for medical therapy in patients with residual disease. Thyrotroph adenomas are rare neoplasms that present with hyperthyroidism and local mass effects. Medical therapy may be effective in controlling tumor growth and in achieving euthyroidism, when surgery or radiation, or both, do not control the tumor.

Pituitary glycoprotein hormone a-subunit secretion by cirrhotic patients

Secretion of the alpha-subunit of pituitary glycoprotein hormones usually follows the secretion of intact gonadotropins and is increased in gonadal failure and decreased in isolated gonadotropin deficiency. The aim of the present study was to determine the levels of the alpha-subunit in the serum of patients with cirrhosis of the liver and to compare the results obtained for eugonadal cirrhotic patients with those obtained for cirrhotic patients with hypogonadotropic hypogonadism. Forty-seven of 63 patients with cirrhosis (74.6%) presented hypogonadism (which was central in 45 cases and primary in 2), 7 were eugonadal, and 9 women were in normal menopause. The serum alpha-subunit was measured by the fluorimetric method using monoclonal antibodies. Cross-reactivity with LH, TSH, FSH and hCG was 6.5, 1.2, 4.3 and 1.1%, respectively, with an intra-assay coefficient of variation (CV) of less than 5% and an interassay CV of 5%, and sensitivity limit of 4 ng/l. The serum alpha-subunit concentration ranged from 36 to 6253 ng/l, with a median of 273 ng/l. The median was 251 ng/l for patients with central hypogonadism and 198 ng/l for eugonadal patients. The correlation between the alpha-subunit and basal LH levels was significant both in the total sample (r = 0.48, P < 0.01) and in the cirrhotic patients with central hypogonadism (r = 0.33, P = 0.02). Among men with central hypogonadism there was a negative correlation between alpha-subunit levels and total testosterone levels (r = -0.54, P < 0.01) as well as free testosterone levels (r = -0.53, P < 0.01). In conclusion, although the alpha-subunit levels are correlated with LH levels, at present they cannot be used as markers for hypogonadism in patients with cirrhosis of the liver.

The use of beta-subunits of gonadotrophin hormones in the follow-up of clinically non-functioning pituitary tumours

OBJECTIVE

Clinically nonfunctioning pituitary adenomas (NFA) are mostly of gonadotroph origin. However, increased levels of circulating hormones or subunits in patients with NFA usually do not cause clinical symptoms, nor are they used as biological tumour markers. In this study we assessed the value of measuring beta subunits of gonadotrophin hormones in the post-operative follow-up of patients bearing these tumours.

DESIGN

Patients harbouring NFA were studied before and three months after transphenoidal pituitary surgery. beta-LH and beta-FSH levels were measured before and following TRH administration on the two occasions. Hormone levels were analyzed in relation to imaging studies performed before and after surgery.

PATIENTS

Twenty four patients operated at the Tel Aviv-Sourasky Medical Centre for NFA.

RESULTS

Pathological beta-FSH and beta-LH levels were detected in 79% and 60% of patients respectively. beta-LH levels decreased after surgery but there were no significant changes in beta-FSH levels. There was a tendency for tumours with high basal beta-LH levels to be larger and to have a poor surgical outcome. Normalization of beta-LH levels post-operatively was usually associated with a decrease in tumour mass or complete removal of the tumour. Persistent pathological responses of beta-LH to TRH after surgery were common in patients with residual tumours on imaging. Nevertheless there were exceptions to this pattern, rendering post-operative beta-LH levels insufficiently reliable as a marker for the presence of residual tumour.

CONCLUSION

Although there appears to be a relationship between beta-LH levels, tumour size and surgical outcome, this association is presently insufficient to allow the routine use of either basal or TRH induced beta-LH responses in the post-surgical follow-up of clinically nonfunctioning pituitary adenomas.

Pathophysiological importance of various molecular forms of human choriogonadotropin

Human chorionic gonadotropin (hCG), its subunits and fragments are widely used for diagnostic purposes. In addition to the diagnosis of pregnancy and pregnancy related disorders, hCG determinations are used for diagnosis of trophoblastic and recently also nontrophoblastic tumors. The use for diagnosis of nontrophoblastic tumors requires highly specific and ultrasensitive assays. With these, it is possible to measure the concentrations of both hCG, the free beta-subunits and the so called beta-core fragment in healthy subjects. Therefore it is important to establish reference values for these and also to be aware of the influence of physiological factors on the serum and urine concentrations. Improved standardization of the assay methods is also essential for these novel applications of hCG determinations to become useful.

Gonadotrophin and free alpha-subunit secretion in patients with acromegaly and clinically non-functioning pituitary tumors: anterior pituitary function and the effect of thyrotrophin-releasing hormone

The effect of the tumor size on the anterior pituitary hypofunction is analyzed in 29 patients with acromegaly and 34 patients with clinically non-functioning pituitary tumor (NFPA). Gonadotrophin and free alpha-subunit (SU) concentrations during daytime variations (samples were taken hourly for 24 h) and after stimulation with TRH were measured as well. Patients with NFPA had a higher prevalence of isolated secondary hypogonadism (20.6% vs 10.3%) and more severe pituitary failure (52.9% vs 6.9%) in comparison with acromegalic patients (p < 0.0001). However, there was no association between the tumor size and the anterior pituitary hypofunction (p = 0.1 and p = 0.9) in patients with NFPA and acromegaly respectively. In premenopausal women and in men with normal/low gonadotrophin levels, mean daytime levels of LH (0.75 +/- 0.6 vs 1.5 +/- 1.9 mlU/ml; p = 0.002) and FSH (2.1 +/- 2.7 vs 4.1 +/- 4.9 mlU/ml; p = 0.009) were higher in patients with acromegaly. There was no difference in the alpha-SU level (p = 0.9). Women with gonadotrophin levels compatible with menopause and men with elevated gonadotrophin levels had the same degree of gonadotrophin and alpha-SU elevation regardless of the tumor type. TRH induced significant rise of LH in 8 (23.5%), FSH in 5 (14.7%) and alpha-SU in 10 (29.4%) patients with NFPA. Among 29 patients with acromegaly LH rose in 6 (20.7%), FSH in 5 (17.2%) and alpha-SU in 3 (10.3%) patients. In conclusion, the anterior pituitary function is better preserved in patients with acromegaly than in patients with NFPA. It seems that the size of pituitary tumor is not the major factor in the pathogenesis of hypopituitarism in patients with macroadenomas. Gonadotrophin and possibly alpha-SU response to TRH exists not only in some patients with clinically non functioning pituitary tumors but also in some patients with acromegaly. Further investigations are need to explain if it represents a biochemical marker of a plurihormonal pituitary tumor in these patients.

Evidence for a trophic action of the glycoprotein hormone alpha-subunit in rat pituitary

The effect of the alpha-subunit of luteinizing hormone (LH alpha) on lactotroph growth in 14-day-old rat pituitary was studied in vitro using a reaggregate pituitary cell culture system. LH alpha significantly expanded both the total population of cells expressing prolactin mRNA and the number of [3H]thymidine incorporating prolactin mRNA expressing cells. No such effect could be elicited by LH. Both effects were inhibited by simultaneous addition of an anti-LH alpha antiserum but not by normal rabbit serum. Anti-LH alpha antiserum added alone to the cultures caused a small decrease in the number of prolactin mRNA expressing cells and in [3H]thymidine labelling of the latter. It is concluded that LH alpha may be a trophic factor of lactotrophs not only during fetal development, as suggested by others previously, but also during the rapid expansion of this cell type during postnatal life in the rat.

Glycoprotein-secreting pituitary adenomas

In the past, pituitary tumours that produce one or more of the glycoproteins (TSH, LH, FSH and alpha subunit) were thought to be rare. However, using modern immunocytochemical and molecular biology techniques, these tumours are being recognized with increasing frequency. Many of these tumours produce glycoprotein alpha and beta subunits in addition to intact glycoproteins. Hormone production is often low compared with tumour size, and serum hormone levels may not be elevated in these patients. Tumours that produce the gonadotrophins (LH or FSH) or alpha subunit account for the majority of clinically non-functioning pituitary adenomas. They do not cause a specific clinical syndrome, and usually present with symptoms of a large mass lesion and/or hypopituitarism. Optimal treatment of these tumours is often difficult. The initial approach is usually transsphenoidal surgery, followed by radiation therapy if there are symptoms due to residual tumour. Medical therapy of gonadotrophin and alpha subunit tumours may include the use of dopamine agonists or somatostatin analogues, although neither has been shown to consistently decrease tumour size. Preliminary trials with experimental GnRH antagonists suggest that these agents may be useful as adjuvant therapy of gonadotrophin tumours. Tumours that produce TSH are rare. Patients present with hyperthyroidism, which is often misdiagnosed as Graves' disease, as well as with symptoms of a pituitary mass lesion. Almost all TSH tumours secrete excess amounts of free alpha subunit. Optimal treatment of these tumours includes transsphenoidal surgery, followed by radiation therapy for residual tumour. The somatostatin analogue octreotide is effective in reducing excess TSH secretion from these tumours, and causes a reduction in tumour volume in a significant minority of patients.

Null cell adenomas, oncocytomas, and gonadotroph adenomas of the human pituitary: An immunocytochemical and ultrastructural anafysis of 300 cases

The immunocytochemical profile of 300 clinically nonsecreting pituitary adenomas was investigated. All tumors were diagnosed, classified, and separated into null cell adenomas, oncocytomas, and gonadotroph adenomas according to their ultrastructural morphology. The immunocytochemical analysis was based on the semiquantitative proportional estimates of positive cells immunostained for all known peptide and glycoprotein pituitary hormones including alpha-subunit. The majority of tumors (87%) were to some extent immunopositive for various hormones. Glycoprotein hormones were most frequently encountered. Usually, particularly in males, more than one subunit was present in the same tumor. In 97 tumors (32%) more than 25% of adenoma cells were immunoreactive for gfycoprotein hormones. Fifty-five tumors (18%) contained occasional cells immunopositive for growth hormone (GH), prolactin (PRL), and adenocorticotropin (ACTH) in addition to glycoprotein hormones. Given the significant proportion of immunoreactive cells for gonadotropins and alpha-subunit, in tumors characterizedas null cell adenomas and oncocytomas, imrnunocytochemistry may provide valuable information to the pathologist and clinical endocrinologist contributing to the evaluation of this heterogeneous group of tumors.

In vitro detection of glycoprotein production and secretion by human nonfunctioning pituitary adenomas

This study, carried out on 9 nonfunctioning pituitary adenomas, was undertaken in order to evaluate the ability of these tumors to synthesize and release gonadotropins and/or free alpha-subunit (alpha-SU) of glycoproteins. The morphological study included electron microscopy and immunofluorescence analysis while hormone release was evaluated by the reverse hemolytic plaque assay (RHPA) and measurements in culture media. By electron microscopy in all tumors (6 null cell adenomas and 3 oncocytomas), it was possible to identify rough endoplasmic reticulum, Golgi apparatus and secretory granules. By immunofluorescence, 5 of 6 tumors were immunoreactive for one or more gonadotropin subunits; in particular, 5 adenomas were positive for alpha-SU and LH-beta, and 3 for FSH-beta. By the RHPA, about 1% of cells obtained from one single tumor formed plaques for LH-beta and alpha-SU while the remaining tumors were negative. Similarly, the study of media concentrations of LH, FSH and alpha-SU in 2 h culture revealed very low amounts of released hormones. In these experimental conditions no modification was observed after the addition of stimulatory agents such as TRH, GnRH and VIP. The present study clearly indicates that although the large majority of nonfunctioning tumors are positive for gonadotropins their secretory capacity is very low in both basal and stimulated conditions.

Pituitary adenoma proliferative indices and risk of recurrence

Twenty unselected pituitary adenomas have been examined for proliferative indices (PIs), and anterior pituitary hormone expression. All but two of the tumours were non-functional with proliferative indices from less than 0.1 to 0.5%. Two tumours were null cell adenomas with PIs less than 0.1 and 0.2%. The PIs of the three recurrent tumours was less than 1.0%. Gonadotrophin and TSH immunoreactivity was heterogenous and was found in 12/20 (60%) of the tumours. There was no significant relationship between PI, hormone expression or any other measured parameter. The biological behaviour of pituitary adenomas with a PI of less than 0.1% is uncertain, but those with a PI of greater than 0.1% are more likely to recur although longer follow-up is needed to confirm this.

HGH, PRL and beta HCG/beta LH gene expression in clinically inactive pituitary adenomas detected by in situ hybridization

Within our surgical collection clinically inactive pituitary adenomas represent 30.7% of all pituitary tumours. To characterize their endocrine activity we studied 40 clinically inactive pituitary adenomas with in situ hybridization (ISH) using cRNA probes labelled with 35S encoding growth hormone (GH), prolactin (PRL) and chorionic gonadotrophin (beta HCG). No tumour was associated with clinical evidence of elevated hormone secretion. A mild hyperprolactinaemia not correlated with hormone or the mRNA content of the cells was interpreted to be incidental in 11 patients. By histological analysis, immunohistochemistry (IH) and electron microscopy the adenomas were diagnosed as small cell chromophobic (n = 16) and large cell chromophobic (n = 8) adenomas, and oncocytomas (n = 16). Gene expression of one or more hormones was identified by ISH in 18 of 40 adenomas in few cells. GH and PRL gene expression was rare (GH mRNA in 3 of 40 tumours and PRL mRNA in 8 of 40 tumours) whereas in 14 of 40 adenomas beta HCG/beta LH gene expression was identified in scattered cells. Five of 40 adenomas lacking hybridization signals revealed hormones by IH. The detection of mRNA was accompanied by positive immunostaining for the respective hormones in 72%. The combination of ISH and IH reveals good evidence that the hormones are synthesized in the tumours and not taken up from the serum and stored in the cells. The two methods used together permit a more precise analysis of tumour biology than each alone.

Clinically nonfunctioning pituitary tumors are monoclonal in origin

Clinically nonfunctioning pituitary adenomas are benign neoplasms comprising approximately 25-30% of pituitary tumors. Little is known about the pathogenesis of pituitary neoplasia. Clonal analysis allows one to make the important distinction between a polyclonal proliferation in response to a stimulatory factor versus a monoclonal expansion of a genetically aberrant cell. We investigated the clonal origin of pituitary tumors using X-linked restriction fragment length polymorphisms at the phosphoglycerate kinase and hypoxanthine phosphoribosyl-transferase genes. Restriction enzymes were used to distinguish maternal and paternal X-chromosomes, and combined with a methylation-sensitive restriction enzyme to analyze allelic X-inactivation patterns in six pituitary adenomas. All six tumors showed a monoclonal pattern of X-inactivation. These data indicate that nonfunctioning pituitary adenomas are unicellular in origin, a result consistent with the hypothesis that this tumor type is due to somatic mutation.

Confounding factors in the interpretation of gonadotropin and gonadotropin-subunit release from cultured human pituitary adenomas

Culture data of 31 human pituitary non-functioning adenomas and effects of cross-reactivity and in vitro culturing conditions on immunoreactivity of gonadotropins and subunits were investigated. Using immunoradiometric assays for FSH and LH and radioimmunoassays for alpha-subunit and LH beta-subunit crossreactivities were reduced to a minimum. Repeated freezing and thawing had no effect on immunoreactivity of hormones and subunits tested. Incubation at 37 degrees C did not affect the immunoreactivity of purified subunit preparations and no recombination of alpha-subunit and LH beta into intact LH could be demonstrated after coincubation of the subunits. FSH immunoreactivity in culture media from 3 pituitary tumors was not affected by incubation at 37 degrees C. LH from a purified preparation and LH in culture media from 3 pituitary adenomas showed a rapid decrease of LH immunoreactivity when left at 37 degrees C. Concomitant with decreasing LH levels at 37 degrees C, a rise in the concentration of alpha-subunit occurred. A direct correlation between gain in alpha-subunit and loss of LH was found. LH beta levels remained stable while LH decreased. This observation may be attributed to an increase in LH beta levels which is compensated by the loss of LH, which has a relatively high crossreactivity in the LH beta immunoassay. LH, FSH, alpha-subunit, LH beta or a combination of these glycoproteins could be demonstrated in 26 out of 31 cultured tumours from patients operated upon because of a clinically non-functioning adenoma. In none of the media of 15 adenomas in which both alpha-subunit and LH were detected, could alpha-subunit levels have been caused by dissociation of LH at 37 degrees C. In two cases, measured LH levels could have been caused by crossreactivity of alpha-subunit and FSH. It was concluded that: (1) in research of non-functioning pituitary adenomas data on gonadotropin and gonadotropin-subunit secretion may suffer from bias caused by crossreactivity; (2) that dissociation of LH into subunits at 37 degrees C is relatively unimportant in in vitro research of non-functioning adenomas; (3) that virtually all non-functioning pituitary adenomas contain or release gonadotropins and/or subunits.

Expression of the alpha subunit of human chorionic gonadotropin in normal and neoplastic neuroendocrine cells. An immunohistochemical study

The alpha subunit of human chorionic gonadotropin (HCG) was localized Immunohistochemically in paraffin sections of normal human tissues and neuroendocrine tumors. A small subset of dispersed neuroendocrine cells was positive in normal adult tissues, including gastric antrum, urachal remnant, anal glands and prostate. Positive cells were consistently present in perinatal lung but rare in adult lung. In contrast, the beta subunit was absent from these cells. Seventy-two of 151 extrapituitary neuroendocrine tumors (48%) were alpha subunit-positive. Thirty-three of 37 bronchial carcinoids (92%) were immunoreactive, with a high percentage of the tumors (54%) containing moderate to large numbers of positive cells. The alpha subunit was further demonstrated in 9 of 45 small cell lung carcinomas (20%), 19 of 35 extrapulmonary carcinoids (54%), 3 of 11 islet cell tumors (27%) and 8 of 13 medullary thyroid carcinomas (62%). Two of three malignant islet cell tumors were positive. Positive cells were usually few in number, except for two small cell lung carcinomas, two rectal carcinoids, one thymic carcinoid and one malignant islet cell tumor. Pheochromocytomas (n = 10) were negative. Eleven of 19 pulmonary tumorlets (58%) were alpha subunit-immunoreactive. A few beta subunit-positive cells were detected in only 6 lung lesions. The physiological significance of the imbalance of expression of HCG subunits by certain neuroendocrine cells and their tumors remains unknown.

Random and Non-Random Coincidence Between Luteinizing Hormone Peaks and Follicle-Stimulating Hormone, Alpha Subunit, Prolactin and Gonadotropin-Releasing Hormone ulsations

Abstract We have examined the co-pulsatility of luteinizing hormone (LH) and prolactin, LH and follicle-stimulating hormone (FSH), and LH and alpha subunit in normal men. We tested whether the degree of physiologically observed co-pulsatility (peak coincidence) significantly exceeded expected random concordance between independently pulsating hormone series. To this end, computer simulations were used to create synthetic endocrine time series pulsating randomly and independently at known frequencies. Resultant predictions of the mean, variance and probability distribution of the number of randomly coincident peaks permitted us to test the null hypothesis that physiologically observed hormone co-pulsatility was due to chance peak associations alone. Physiological observations were made in 33 normal men and in six ovariectomized ewes subjected to combined hypothalamo-pituitary and jugular venous catheterization. The following salient results were obtained: 1) random peak coincidence rates between independently pulsating hormone series were substantial at high pulse frequencies, but such random rates were significantly exceeded in the case of gonadotropin-releasing hormone and LH peaks (P< 0.0001); 2) random coincidence was further increased when coincidence was defined as peak maxima occurring not only simultaneously but also within some defined time window (e.g. +/-10 min, as commonly done in the literature); 3) significant co-pulsatility could be demonstrated for simultaneous LH and FSH pulsations in normal men (P< 0.0001); 4) coincidence rates for 10-min lagged (but not for simultaneous) LH and prolactin pulses were significantly more likely than chance associations; 5) observed coincidence between LH and a subunit pulses significantly exceeded expected (random) peak overlap (P<0.001); and 6) in contrast, hormone peaks in different men were only randomly associated. We conclude that based upon the means, variances and probability distributions calculated here, available reports on peak coincidence between pulsatile neuroendocrine time series must be re-examined in the light of high rates of random coincidence observed between independently pulsating hormone series.

Fluorescence histochemistry of RNA in human pituitary adenomas

Acridine orange (AO)-RNA fluorescence was studied histochemically in 9 normal human pituitary glands, in 26 secretory and nonsecretory pituitary adenomas, and in a dysgerminoma. Six adenomas showing immunoreactivity for prolactin showed intense orange-red cytoplasmic fluorescence; 6 other tumours exhibiting immunoperoxidase activity of growth hormone showed less intense AO-RNA fluorescence, and 5 adrenocorticotropic hormone-containing adenomas showed still weaker orange fluorescence. Among the chromophobe adenomas without immunoreactivity for secretory products, 5 had uniformly very weak AO-RNA fluorescence, while in 4 other a few scattered cells with strong AO-RNA fluorescence were detected among the majority of weakly fluorescent cells. The pituitary dysgerminoma contained many cells with strong AO-RNA fluorescence. Electron microscopy of these cases showed good correlation of cytoplasmic concentration of ribosomes with AO-RNA fluorescence of the adenomas. AO is useful as an inexpensive, simple supplementary stain for frozen or paraffin sections of pituitary tumours to infer secretory activity as a correlate of RNA concentration and to demonstrate a secretory potential in some cells of hormonally inactive tumours.

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.

Release of gonadotropin alpha subunit from rat pituitary cultures in response to GnRH

Gonadotropin releasing hormone (GnRH)-stimulated release of the alpha subunit common to the gonadotropins and to thyrotropin was studied in rat pituitary cell cultures. In these studies we took advantage of a recently prepared antiserum specific for the alpha subunit. We show that pituitary cells treated with GnRH released alpha subunit in a similar pattern to intact luteinizing hormone (LH) during short-term incubations (0-12 h); during prolonged incubations (12-48 h), however, release of alpha subunit did not desensitize in response to the releasing hormone and the pattern became different from that measured for intact LH. Further, we assessed the relative requirement for Ca2+ in the release of LH and alpha subunit. When pituitary cells were treated with 10(-8) M GnRH in the presence of a range of concentrations of the Ca2+ ion channel antagonist, methoxyverapamil (D-600), release of both LH and alpha subunit was inhibited in a similar and dose-dependent manner; 10(-4) M D-600 showed maximum inhibitory efficacy (IC50 = 10(-5) M). The calmodulin antagonist, pimozide, also inhibited both GnRH-stimulated LH and alpha subunit release (IC50 = 0.75 microM). These data suggested that although the Ca2+/calmodulin system appears to mediate both the release of LH and alpha subunit in response to GnRH, these processes appear differentially regulated during long-term exposure to the releasing hormone.

Immunohistochemical studies of human FSH producing pituitary adenomas

Ten FSH producing pituitary adenomas were studied immunohistochemically. 9 cases were in males, and 7 showed elevated serum FSH levels. Immunohistochemically, all cases showed the presence of alpha-subunit and FSH-beta subunits in many tumour cells. These two subunits were frequently colocalized in the same cells. However, the expression of LH-beta subunit was extremely low (1 of 10 cases exhibiting occasional LH-beta positive tumour cells), although it has been reported that FSH-beta and LH-beta subunits are colocalized in the same cells of the normal adult pituitary gland. Immunoelectron microscopically, alpha-subunits and FSH-beta were present in the secretory granules and suggested the co-release of subunits or secretion of combined form of FSH. In 7 cases, TSH-beta was positive, and in some cases, TSH-beta was colocalized in the same tumour cells which contained alpha-subunit and FSH-beta subunit. A few cases also demonstrated immunoreactivity for PRL and ACTH. Our immunohistochemical studies suggest that FSH adenomas are multihormonal and that there is abnormal gene expression in FSH cells with loss of LH-beta appearance and co-expression of TSH-beta.

Glycoprotein hormone genes are expressed in clinically nonfunctioning pituitary adenomas

Approximately 25% of patients with pituitary adenomas have no clinical or biochemical evidence for excess hormone secretion and are classified as having null cell or nonfunctioning adenomas. To characterize the cell type of these tumors, we analyzed pituitary hormone gene expression in clinically nonfunctioning pituitary adenomas using specific oligonucleotide probes for the messenger (m)RNAs encoding growth hormone, prolactin, ACTH, and the glycoprotein hormone subunits, alpha, luteinizing hormone (LH)beta, follicle-stimulating hormone (FSH)beta, and thyroid-stimulating hormone (TSH)beta. Expression of one or more of the anterior pituitary hormone genes was found in 12/14 (86%) of the patients with clinically classified nonfunctioning adenomas. Expression of one or more of the glycoprotein hormone genes (alpha, LH beta, FSH beta, TSH beta) was identified most commonly (79%) with expression of multiple beta-subunit genes in many cases. Expression of alpha-subunit mRNA was found in each of the adenomas from patients expressing one of the beta-subunit mRNAs and in three patients with no detectable beta-subunit mRNA. Although FSH beta and LH beta mRNAs were found with similar frequencies in nonfunctioning adenomas, expression of FSH beta mRNA was generally much more abundant. TSH beta mRNA was detected in only one adenoma. The levels of glycoprotein hormone subunit mRNAs were variable in different adenomas, but the lengths of the mRNAs and transcriptional start sites for the alpha- and beta-subunit genes were the same in the pituitary adenomas and in normal pituitary. Growth hormone and prolactin gene expression were not observed in the nonfunctioning adenomas, but ACTH mRNA was found in a single case. Immunohistochemistry of the adenomas confirmed production of one or more pituitary hormones in 13/14 (93%) nonfunctioning tumors, with a distribution of hormone production similar to that of the hormone mRNAs. These data indicate that pituitary adenomas originating from cells producing glycoprotein hormones are common, but are difficult to recognize clinically because of the absence of characteristic endocrine syndromes and defective hormone biosynthesis and secretion.

Hormone production in clinically nonfunctioning pituitary adenomas

Pituitary tumors in which no excess hormone secretion can be identified clinically have been considered as nonfunctioning or null-cell adenomas. Immunocytochemical data presented here suggest that many of these tumors contain subunits of the glycoprotein hormones. Of 160 patients referred for pituitary surgery, 37 (23%) had no evidence of excess hormone secretion on preoperative endocrine evaluation. Immunocytochemical staining of these tumors was carried out using antibodies specific for prolactin, growth hormone, adrenocorticotropic hormone, the beta subunits of luteinizing hormone (beta-LH), follicle-stimulating hormone (beta-FSH), and thyroid-stimulating hormone (beta-TSH), and the alpha subunit. One or more of these pituitary hormones were detected in 73% of cases. The alpha and beta subunits were detected most frequently, being found in 68% of cases; 27% had staining for one or more beta subunits and 37.9% had staining for both alpha and beta subunits. The incidence was: beta-FSH in 58%, beta-LH in 47%, beta-TSH in 33%, and the alpha subunit in 42%. Staining for multiple glycoprotein hormones was common (52%), and mixed glycoprotein hormones and prolactin cell types were found in 16% of cases. These data suggest that most apparently nonfunctioning pituitary tumors contain immunoreactive hormones and the majority of these are subunits of the glycoprotein hormones. Since the glycoprotein hormone beta subunits must combine with the alpha subunit to produce biologically active hormones, the production of the subunits alone may not have endocrine manifestations.

Growth hormone secreting pituitary adenomas are heterogeneous in cell culture and commonly secrete glycoprotein hormone alpha-subunit

Cell culture methods were used to assess whether human pituitary adenomas secreting GH and associated with clinical acromegaly also secreted the structurally unrelated glycoprotein hormone alpha-subunit. Thirty-two tumours, together with peri-adenomatous tissue from two of them and three normal pituitaries were studied. Anterior pituitary hormones were measured by radioimmunoassay and included PRL, TSH, LH, FSH, and ACTH, as well as GH and alpha-subunit. Normal pituitary tissues secreted all hormones assayed. All 32 tumours secreted GH ranging from 241 to 5556 ng/2 X 10(5) cells/24 h and 12 (37.5%) secreted alpha-subunit in amounts which could not be accounted for by cross-reaction of other hormones or contamination by normal pituitary tissue, and which ranged from 10.3 to 73.5 ng/2 X 10(5) cells/24 h. Ten other tumours also secreted alpha-subunit but in very small amounts, not exceeding 1.8 ng/2 X 10(5) cells/24 h. PRL was secreted from 21 tumours (66%), and small amounts of other hormones, chiefly LH and TSH, were occasionally secreted from tumours. These cell culture studies would suggest that pituitary adenomas causing acromegaly are hormonally heterogeneous and that PRL and glycoprotein alpha-subunit are commonly detected in addition to GH.

Endocrine impact of pure estradiol replacement in postmenopausal women: alterations in anterior pituitary hormone release and circulating sex steroid hormone concentrations

Thirteen healthy postmenopausal volunteers were studied under basal conditions and at intervals (days 1, 5, 10, and 30) after intravaginal placement of a polysiloxane ring impregnated with 400 mg of estradiol. Mean serum estradiol concentrations rose 26-fold with a twofold increase in serum estrone concentrations. Serum delta 4-androstenedione, dehydroepiandrosterone sulfate, and total testosterone did not change, but absolute and percent free testosterone concentrations declined significantly by day 5. Concurrently, serum concentrations of immunoactive follicle-stimulating hormone declined progressively, while serum luteinizing hormone and free alpha-subunit concentrations exhibited a biphasic pattern of suppression. Serum levels of prolactin increased monophasically and those of growth hormone, somatomedin C, and thyroid-stimulating hormone did not change.

Alpha-subunit-producing pituitary adenomas. Immunocytochemical and ultrastructural studies

Immunohistological techniques demonstrate the alpha-subunit of glycoprotein hormones in the majority of endocrine-inactive, undifferentiated pituitary adenomas and pituitary oncocytomas. In about one-fifth of endocrine-active adenomas, the alpha-subunit is produced in combination with either adrenocorticotropic hormone or prolactin, and it is found in combination with growth hormone in about half of those adenomas causing acromegaly. Pure alpha-subunit-producing, endocrine-inactive adenomas characteristically have small secretory granules that are destroyed by direct osmium fixation, but are well preserved after prefixation with glutaraldehyde. As only a few atypical prolactinomas show similar secretory granules, and as they display a positive reaction for the alpha-subunit only exceptionally, this ultrastructural feature can serve as a guide to differentiate such adenomas.

Pure alpha-subunit producing tumor derived from a thyrotropic tumor: impaired regulation of alpha-subunit and its mRNA by thyroid hormone

We have recently described a mouse pituitary tumor line which produces only the alpha-subunit of the glycoprotein hormones. This tumor line may be a useful animal model to study autonomous pituitary tumors which secrete only alpha-subunit. Our pure alpha-subunit producing tumor was derived from a thyrotropic tumor which secreted intact TSH as well as free alpha-subunit. Our current studies compare the regulation of alpha-subunit biosynthesis in a conventional thyrotropic tumor and the alpha-subunit producing tumor. Thyroxine or triiodothyronine administration to mice bearing the alpha-subunit producing tumor resulted in no change in plasma alpha-subunit concentration, and a 10-19% reduction in tumor alpha-subunit mRNA concentration that was not statistically significant. In contrast, thyroxine administration to mice bearing the thyrotropic tumor resulted in an 81% reduction in plasma alpha-subunit concentration, and a 75% reduction in tumor alpha-subunit mRNA concentration (P less than 0.01). Other studies using a cDNA specific for thyrotropin-beta (TSH beta) failed to detect TSH beta mRNA in the alpha-subunit producing tumor, while TSH beta mRNA was easily detected in the conventional thyrotropic tumor. We conclude that during the development of the alpha-subunit producing tumor from a thyrotropic tumor, loss of TSH beta mRNA was also associated with an impaired capacity for thyroid hormone to decrease concentrations of alpha-subunit mRNA.

Gonadotrophin-secreting pituitary tumour: report and review

A 34-year-old male with a pituitary adenoma was investigated and demonstrated to have hypersecretion of both gonadotrophins in the basal state. Immunocytochemical staining and electron microscopic examination were positive for tumour cells secreting FSH and LH. Presenting symptoms included visual disturbances, loss of libido, impotence, cold intolerance, frontal headaches, change in skin pigmentation and excessive weight gain. The patient denied alteration in hair distribution, had no acral features, galactorrhoea or gynaecomastia. Surgical extirpation resulted in complete amelioration of his symptoms over a three year follow-up period. Basal and stimulated pituitary function testing results returned to normal post-operatively. A review of the literature documents six other cases of pituitary tumour secreting both LH and FSH in the basal state. More commonly, the pituitary adenoma secretes FSH only. The literature is reviewed with regard to both types of tumour.

The levels and subcellular distribution of hormones and marker enzymes in pituitaries from control subjects and patients with prolactinomas, acromegaly or functionless pituitary tumours

Pituitary homogenates were prepared from patients undergoing pituitary ablation for breast or prostatic carcinoma (controls) and from patients with either PRL- and GH-secreting pituitary adenomas or from patients with 'functionless' pituitary tumours. The principal subcellular organelles, plasma membrane, lysosomes, mitochondria, endoplasmic reticulum, cytosol and hormone-containing granules were characterized by sucrose density gradient centrifugation. Tissue from patients with prolactinomas showed hormone granules, lysosomes and endoplasmic reticulum of lighter density than controls; cytosol, mitochondria and plasma membrane were similar. PRL-secreting tumours showed a 2-fold increase in PRL content with significant reduction of LH, FSH and GH. Activities of various lysosomal enzymes, except for PRL proteolytic activity, were significantly reduced. Similar conclusions were found for GH-secreting pituitary adenomas with a striking reduction in PRL proteolytic activity. Functionless tumours showed significant amounts, though reduced compared to control tissue, of all hormones. In contrast to the hormone-secreting adenomas, the activity of the lysosomal enzyme N-acetyl-beta-glucosaminidase was significantly increased compared to control tissue.

Effect of hyperprolactinemia and age on the hypogonadism of uremic men on hemodialysis

Primary hypogonadism has been commonly reported among uremic men on hemodialysis, characterized by low testosterone levels, increased luteinizing hormone and sometimes follicle-stimulating hormone levels. Little is known about the influence of hyperprolactinemia and age on this hypogonadism. In 149 hemodialysis patients and in 60 healthy subjects the serum levels of testosterone (T), gonadotropins (LH and FSH) and prolactin (PRL) were assessed through radioimmunoassay. Mean +/- SD hormone levels were: T 274 +/- 125 ng/100 ml, lower than controls; LH 44.7 +/- 46.1 mlU/ml and FSH 17.6 +/- 18.4 mIU/ml, both higher than controls. PRL 31.3 +/- 49.4 ng/ml, higher than controls. A positive correlation between LH and FSH, a negative correlation between PRL and both T and LH was found. Moreover T and FSH were correlated with age only in the normoprolactinemic patients. These data suggest: a common damaging mechanism by uremia on both interstitial and tubular structures of the testis; a central antigonadal influence of hyperprolactinemia even if a direct action on the testis cannot be excluded; a worsening action of age on the gonadal function of these patients.

Investigation of hypothalamic-pituitary disease

It can be readily appreciated from the preceding discussion that many endocrine and non-endocrine tests are available for the evaluation of patients with suspected hypothalamic-pituitary disease. The endocrine evaluation of these subjects should be tailored according to the type and extent of pathology suspected (see Tables 2 and 3). For patients with pituitary adenomas and clinical features of hyperpituitarism, such as hyperprolactinaemia, Cushing's disease or acromegaly, the initial tests should be directed at the hormone whose excess is suspected. For example, a glucose suppression test for acromegaly or dexamethasone suppression test for Cushing's disease should be performed early in the evaluation. The possibility of deficiencies of the other pituitary hormones should then be addressed in patients with secretory tumours, but initially in those with apparent non-functioning adenomas. In patients with large macroadenomas pituitary hormone deficiencies are almost invariable with GH and FSH/LH being the most commonly affected, followed by TSH and ACTH in that order (Snyder et al, 1979a; Valenta et al, 1982). Basal thyroid function tests, serum oestradiol or testosterone, and basal gonodotrophins should be routinely obtained in patients with macroadenomas. Additionally, the integrity of the pituitary-adrenal axis should be determined and an overnight water deprivation test for assessment of neurohypophyseal function is also recommended. GH stimulation testing is valuable as a test of pituitary function in patients with suspected pituitary tumours since GH reserve is lost very early in the development of hypopituitarism. Evaluation of the pituitary-thyroid axis with TRH or the pituitary gonadal axis with LHRH generally provides limited additional information of diagnostic value in individual patients with macroadenomas. However, the 'paradoxical' responses to TRH and LHRH may be useful as a biological marker following therapy in patients with GH- or ACTH-secreting tumours. In patients with microadenomas, pituitary hormone deficiencies are uncommon (Valenta et al, 1982). Despite this observation, it may be beneficial to determine basal thyroid levels, gonadotrophin levels, serum testosterone or oestradiol levels, and the response to an overnight metyrapone test in such patients to provide a baseline for future care.(ABSTRACT TRUNCATED AT 400 WORDS)

Pure alpha subunit-secreting pituitary tumors

The authors describe six patients with pituitary macroadenomas hypersecreting only the alpha subunit of the glycoprotein hormones. These patients had been previously diagnosed as having "non-functioning chromophobe adenomas." All of the patients had visual field abnormalities and partial hypopituitarism. The elevated serum alpha concentrations showed a variable response to stimulation by thyrotropin-releasing hormone, and could not be suppressed by thyroid hormone administration. Immunological, gel chromatographic, and immunocytochemical studies documented that only the alpha subunit was present. Following pituitary surgery and radiotherapy, serum alpha levels decreased. These patients represent a new subset of functioning pituitary tumors. Determination of alpha subunit concentration is useful in managing some patients with pituitary tumors previously thought to have non-functioning chromophobe adenomas.

Dopaminergic modulation of TSH and its subunits: in vivo and in vitro studies

We have studied the effects of dopamine on the secretion of TSH and its subunits in vivo and in vitro. Four normal controls, seven patients with primary hypothyroidism, two patients with peripheral resistance to thyroid hormone (PRTH), and two patients with alpha-secreting pituitary tumours underwent a 3-h dopamine infusion (4 micrograms/kg/min). Serial blood samples were drawn for TSH, PRL, alpha, and TSH-beta subunit. In normal subjects, TSH fell from 2.1 +/- 0.9 (+/- SE) to 0.7 +/- 0.1 microU/ml (P less than 0.05), and alpha declined from 1.5 +/- 0.4 to 1.0 +/- 0.1 ng/ml (P less than 0.01). TSH-beta was at or slightly above the detection limits of the assay before and after dopamine. In hypothyroidism, basal serum TSH was 81 +/- 14 microU/ml. With dopamine, TSH fell to 35 +/- 8 microU/ml (P less than 0.001), while alpha decreased from 3.2 +/- 0.4 to 2.0 +/- 0.3 ng/ml (P less than 0.01). Serum TSH-beta also declined from 0.97 +/- 0.06 to 0.57 +/- 0.05 ng/ml (P less than 0.001). A similar fall in TSH and alpha was seen in the two patients with PRTH. In normals and hypothyroid patients, the percentage change in alpha concentration was significantly less than that observed for intact TSH. This is due presumably to the contribution of the gonadotrophs to the circulating alpha pool. TSH and TSH-beta were undetectable in the two pituitary tumour patients, and alpha declined only slightly in each patient after dopamine. The in vitro effects of dopamine were studied using cultured bovine anterior pituitary cells. Dopamine (10(-4)-10(-8) mol/l) did not change basal TSH, alpha, or TSH-beta release. However, dopamine at all doses significantly blunted TRH (10(-7) mol/l)-stimulated TSH and TSH-beta release, and blunted TRH-mediated alpha release at the two highest dopamine doses. These data suggest that dopamine modulates both TSH and TSH subunit secretion. These effects may be exerted directly at the level of the thyrotroph.

Glycoprotein-hormone alpha-chain production by pancreatic endocrine tumors: a specific marker for malignancy. Immunocytochemical analysis of tumors of 155 patients

Human chorionic gonadotropin (hCG) or its alpha- and beta-subunits have been proposed as specific quantitative markers for malignant pancreatic endocrine tumors. Since proof of malignancy of pancreatic endocrine tumors is difficult early in the course of the illness, we tested retrospectively a series of 157 pancreatic endocrine tumors of 155 patients for alpha- or beta-subunits of hCG by immunocytochemistry. Human CG-alpha-immunoreactive cells were present in 42 of 56 (75%) functioning malignant pancreatic endocrine tumors but in only one, possibly benign, glucagonoma of 67 functioning benign tumors, in only one of 17 nonfunctioning malignant and in none of 17 nonfunctioning benign tumors. No beta-hCG-immunoreactivity was localized in the tumors. Human CG-alpha appears to be a reliable quantitative and qualitative marker for malignancy in functioning pancreatic endocrine tumors.

Alpha and beta subunits of glycoprotein hormones in argyrophil pituitary tumors with small granule cells

A group of 33 functionless pituitary tumors with small argyrophil groups (SAG) were collected from a series of 200 pituitary adenomas (16.5% of all adenomas). Histologically, the tumors showed an unusually high frequency of trabecular patterns, perivascular pseudo-rosettes, and oncocytoid transformation. Immunoreactivity for glycoprotein hormone alpha-chain was found in more or less numerous cells of 20 cases (64.5% of SAG tumors). Thirteen of these cases also showed specific beta-chain immunoreactivity, especially for follicle-stimulating hormone (FSH) beta-chain, which was present in 11 tumors. Various admixtures of immature, oncocytic, sparsely granulated, and densely granulated cells were observed ultrastructurally, with prevalence of the latter cell variants in tumors showing immunoreactive cells and prevalence of the former cell variants in tumors lacking immunoreactive cells. It is suggested that some relationship may exist between SAG cell (glycoprotein hormone precursor cells?) tumors--or at least part of them--and glycoprotein hormone cell lines. Anyway, whatever their origin and interpretation, SAG cell tumors seem to represent a distinct clinicopathologic entity.