Italian Association of Clinical Endocrinologists (AME) and International Chapter of Clinical Endocrinology (ICCE). Position statement for clinical practice: prolactin-secreting tumors

Prolactinomas are the most frequent pituitary adenomas. Prolactinoma may occur in different clinical settings and always require an individually tailored approach. This is the reason why a panel of Italian neuroendocrine experts was charged with the task to provide indications for the diagnostic and therapeutic approaches that can be easily applied in different contexts. The document provides 15 recommendations for diagnosis and 54 recommendations for treatment, issued according to the GRADE system. The level of agreement among panel members was formally evaluated by RAND-UCLA methodology. In the last century, prolactinomas represented the paradigm of pituitary tumors for which the development of highly effective drugs obtained the best results, allowing to avoid neurosurgery in most cases. The impressive improvement of neurosurgical endoscopic techniques allows a far better definition of the tumoral tissue during surgery and the remission of endocrine symptoms in many patients with pituitary tumors. Consequently, this refinement of neurosurgery is changing the therapeutic strategy in prolactinomas, allowing the definitive cure of some patients with permanent discontinuation of medical therapy.

mPRs represent a novel target for PRL inhibition in experimental prolactinomas

Membrane progesterone receptors are known to mediate rapid nongenomic progesterone effects in different cell types. Recent evidence revealed that mPRα is highly expressed in the rat pituitary, being primarily localized in lactotrophs, acting as an intermediary of P4-inhibitory actions on prolactin secretion. The role of mPRs in prolactinoma development remains unclear. We hypothesize that mPR agonists represent a novel tool for hyperprolactinemia treatment. To this end, pituitary expression of mPRs was studied in three animal models of prolactinoma. Expression of mPRs and nuclear receptor was significantly decreased in tumoral pituitaries compared to normal ones. However, the relative proportion of mPRα and mPRβ was highly increased in prolactinomas. Interestingly, the selective mPR agonist (Org OD 02-0) significantly inhibited PRL release in both normal and tumoral pituitary explants, displaying a more pronounced effect in tumoral tissues. As P4 also regulates PRL secretion indirectly, by acting on dopaminergic neurons, we studied mPR involvement in this effect. We found that the hypothalamus has a high expression of mPRs. Interestingly, both P4 and OrgOD 02-0 increased dopamine release in hypothalamus explants. Moreover, in an in vivo treatment, that allows both, pituitary and hypothalamus actions, the mPR agonist strongly reduced the hyperprolactinemia in transgenic females carrying prolactinoma. Finally, we also found and interesting gender difference: males express higher levels of pituitary mPRα/β, a sex that does not develop prolactinoma in these mice models. Taken together, these findings suggest mPRs activation could represent a novel tool for hyperprolactinemic patients, especially those that present resistance to dopaminergic drugs.

Association of prolactin receptor (PRLR) variants with prolactinomas

Prolactinomas are the most frequent type of pituitary tumors, which represent 10-20% of all intracranial neoplasms in humans. Prolactinomas develop in mice lacking the prolactin receptor (PRLR), which is a member of the cytokine receptor superfamily that signals via Janus kinase-2-signal transducer and activator of transcription-5 (JAK2-STAT5) or phosphoinositide 3-kinase-Akt (PI3K-Akt) pathways to mediate changes in transcription, differentiation and proliferation. To elucidate the role of the PRLR gene in human prolactinomas, we determined the PRLR sequence in 50 DNA samples (35 leucocytes, 15 tumors) from 46 prolactinoma patients (59% males, 41% females). This identified six germline PRLR variants, which comprised four rare variants (Gly57Ser, Glu376Gln, Arg453Trp and Asn492Ile) and two low-frequency variants (Ile76Val, Ile146Leu), but no somatic variants. The rare variants, Glu376Gln and Asn492Ile, which were in complete linkage disequilibrium, and are located in the PRLR intracellular domain, occurred with significantly higher frequencies (P < 0.0001) in prolactinoma patients than in 60 706 individuals of the Exome Aggregation Consortium cohort and 7045 individuals of the Oxford Biobank. In vitro analysis of the PRLR variants demonstrated that the Asn492Ile variant, but not Glu376Gln, when compared to wild-type (WT) PRLR, increased prolactin-induced pAkt signaling (>1.3-fold, P < 0.02) and proliferation (1.4-fold, P < 0.02), but did not affect pSTAT5 signaling. Treatment of cells with an Akt1/2 inhibitor or everolimus, which acts on the Akt pathway, reduced Asn492Ile signaling and proliferation to WT levels. Thus, our results identify an association between a gain-of-function PRLR variant and prolactinomas and reveal a new etiology and potential therapeutic approach for these neoplasms.

Nonalcoholic fatty liver disease with prolactin-secreting pituitary adenoma in an adolescent: A case report

RATIONALE

Nonalcoholic fatty liver disease (NAFLD), among the commonest chronic liver disorders in children and adolescents, is considered a reflection of the current obesity epidemic in children and adults. This liver disease has been linked with various metabolic disorders, but not with prolactinoma (PRLoma).

PATIENT CONCERNS

A 13-year-old Japanese girl manifested obesity, serum transaminase and γ-glutamyltransferase elevations, and amenorrhea. Abdominal ultrasonography showed fatty liver. Her serum prolactin concentration was elevated, and cranial magnetic resonance imaging showed a pituitary mass consistent with macroadenoma.

DIAGNOSES

NAFLD and PRLoma.

INTERVENTIONS AND OUTCOMES

After the patient's NAFLD failed to respond to diet and exercise, cabergoline treatment of the PRLoma decreased body weight, serum transaminase and γ-glutamyltransferase elevations, and ultrasonographic fatty liver grade as the tumor became smaller.

LESSONS

Physicians should consider the possibility of PRLoma when diet and exercise fail to improve fatty liver disease in a patient with endocrine symptoms such as amenorrhea.

[Multiple Endocrine Neoplasia I (Wermers Syndrome), Forms of Clinical Manifestation, 5 Case Studies]

Multiple Endocrine Neoplasia (MEN) is a condition in which several endocrine organs of an individual are affected by adenoma, hyperplasia and less often carcinoma, either simultaneously or at different stages of life. Two existing syndromes, MEN1 and MEN2 (2A, 2B), in literature is also mentioned MEN4, are associated also with other non-endocrine disorders. MEN1 (Wermer syndrome) affects the pituitary, parathyroid, and pancreatic area. 95 % of patients show very early manifestation of hyperparathyroidism, often before 40 years of age. Multiple adenomas gradually involve all four parathyroid glands. The first clinical sign of MEN1 includes recurrent nephrolithiasis. The second most frequent manifestation of MEN1 is pancreatic area (pancreas, stomach and duodenum), again multiple malignancies of varying degree which can metastasize. Most often gastrinomas and insulinomas are involved. Pituitary adenomas occur in about one third of MEN1 patients and tend to be larger and less responsive to treatment. Tumors appearing most often are prolactinomas, tumors producing growth hormone, or afunctional adenomas. The other endocrine tumors include carcinoids and adrenal lesions. In the last year we have registered four MEN1 syndrome patients in our center and one patient has been already followed since 2008. In four out of five patients, nephrolithiasis after 30 years of age was the first clinical symptom, but only one of theses cases resulted in MEN1 diagnosis. In all patients, the clinical symptoms intensified and the diagnosis was established between 36 and 40 years of age. A crutial factor is a cooperation with the urology examination of kidney stones formation in young individuals with nephrolithiasis in order to reveal the potential cases of MEN1 syndrome very early on. Consider the MEN1 genetic diagnostics if recurrent primary hyperparathyroidism or recurrent gastroduodenal ulcer disease appear in patients under 40 years of age.Key words: carcinoid - gastrinoma - hyperparathyroidism - insulinoma - MEN1 - multiple endocrine neoplasia - nefrolithiasis - neuroendocrine tumor - pancreatic area - pituitary gland.

Pituitary adenomas in childhood, adolescence and young adulthood: presentation, management, endocrine and metabolic outcomes

OBJECTIVE

To elucidate the long-term outcomes of pituitary adenomas diagnosed in childhood and adolescence, knowledge of which remains sparse.

DESIGN AND METHODS

A retrospective review of patients aged ≤21 years at diagnosis of pituitary adenoma, attending a neuroendocrine service in Liverpool, UK, between 1984-2009.

RESULTS

There were 41 patients (33 female), mean age at diagnosis 17.3 years (range 11-21) and mean follow-up 9.6 years; 29 patients had prolactinomas (15 macroprolactinomas), 6 non-functioning pituitary adenomas (NFPAs), 5 Cushing's disease (CD) and 1 acromegaly. All prolactinoma patients received dopamine agonists (DAs) and three also underwent pituitary surgery. Furthermore, ten patients underwent surgery: five with CD, one with acromegaly and four with NFPA. Four received radiotherapy after surgery. Another ten patients received hormone replacement: nine hydrocortisone, five thyroxine, seven sex steroids and five GH; another seven had severe asymptomatic GH deficiency. Three female patients were treated for infertility (two successfully). Thirteen patients gained significant weight (body mass index (BMI) increase >2 kg/m(2)) since diagnosis and 16 in total are now obese (BMI>30 kg/m(2)). Five were treated with orlistat and one attended a weight management service. Two received antihypertensive medications, two had type 2 diabetes and four were treated for dyslipidaemia.

CONCLUSIONS

This is one of the largest reviews of patients aged 21 or younger at diagnosis of pituitary adenoma followed up by a single service. Two-thirds had prolactinomas, all were treated with DAs and three underwent surgery. Increased cardiovascular risk factors (obesity and dyslipidaemia) and infertility are important sequelae and active identification and treatment are necessary.

Enhanced LH action in transgenic female mice expressing hCGbeta-subunit induces pituitary prolactinomas; the role of high progesterone levels

The etiology of pituitary adenomas remains largely unknown, with the exception of involvement of estrogens in the formation of prolactinomas. We have examined the molecular pathogenesis of prolactin-producing pituitary adenomas in transgenic female mice expressing the human choriongonadotropin (hCG) beta-subunit. The LH/CG bioactivity is elevated in the mice, with consequent highly stimulated ovarian progesterone (P(4)) production, in the face of normal estrogen secretion. Curiously, despite normal estrogen levels, large prolactinomas developed in these mice, and we provide here several lines of evidence that the elevated P(4) levels are involved in the growth of these estrogen-dependent tumors. The antiprogestin mifepristone inhibited tumor growth, and combined postgonadectomy estradiol/P(4) treatment was more effective than estrogen alone in inducing tumor growth. Evidence for direct growth-promoting effect of P(4) was obtained from cultures of primary mouse pituitary cells and rat somatomammotroph GH3 cells. The mouse tumors and cultured cells revealed stimulation of the cyclin D1/cyclin-dependent kinase 4/retinoblastoma protein/transcription factor E2F1 pathway in the growth response to P(4). If extrapolated to humans, and given the importance of endogenous P(4) and synthetic progestins in female reproductive functions and their pharmacotherapy, it is relevant to revisit the potential role of these hormones in the origin and growth of prolactinomas.

Pituitary tumours: the prolactinoma

This review focus on the epidemiology, diagnosis and treatment of prolactinomas. In particular, attention was given to recent data showing a high prevalence of these tumours in the general population, 3-5 times higher than previously reported. The diagnosis of hyperprolactinaemia has been simplified in recent years, and only prolactin (PRL) assay and magnetic resonance imaging of the sella are required. Nonetheless, macroprolactinaemia should be assessed in patients with hyperprolactinaemia in the absence of clinical symptoms of elevated PRL levels. The recent evidence that medical therapy with dopamine agonists should be continued lifelong has been confirmed by several studied. The patients achieving disappearance of the tumours and suppression of PRL levels during treatment are those showing the highest likelihood to have persistent remission of hyperprolactinaemia after treatment withdrawal.

Hyperprolactinaemia

Hyperprolactinaemia is a common condition with varied aetiology. It is more frequent in women, but also seen in men and even in adolescence and childhood. Prolactin is mainly a lactogenic hormone but has other actions. Most cases present with amenorrhoea and infertility and are managed by gynaecologists. However, multidisciplinary involvement may be required in some cases. Evidence relating to aetiology, clinical features, pathogenesis and management has been discussed.

Simultaneous above and below approach to giant pituitary adenomas: surgical strategies and long-term follow-up

INTRODUCTION

Giant pituitary adenomas of excessive size, fibrous consistency or unfavorable geometric configuration may be unresectable through conventional operative approaches. We present our select case series for operative resection and long-term follow-up for these unusual tumors, employing both a staged procedure and a combined transsphenoidal-transcranial above and below approach.

METHOD

A retrospective chart review was performed on patients operated via the staged, and combined approaches by the senior author (J.N.B.). Preoperative characteristics and postoperative outcomes were reviewed. A detailed description of the operative technique and perioperative management is provided.

RESULTS

Between 1993 and 1996, two patients harboring giant pituitary adenomas underwent an intentionally staged resection, and between 1997 and 2006, nine patients harboring giant pituitary adenomas underwent surgery via a single-stage above and below approach. Nine patients (82%) presented with non-secreting adenomas and two patients (18%) presented with prolactinomas refractory to medical management. Gross total resection was achieved in six patients (55%), near total resection in 1 (9%), and subtotal removal in 4 (36%). Seven patients (64%) experienced visual improvement postoperatively and no major complications occurred. Long-term follow-up averaged 51.6 months. Panhypopituitarism was observed in four patients, partial hypopituitarism in four, persistent DI in two, and persistent SIADH in one.

CONCLUSIONS

The addition of a transcranial component to the transsphenoidal approach offers additional visualization of critical neurovascular structures during giant pituitary adenoma resection. Complications rates are similar to other series in which complex pituitary adenomas are resected by other means. The above and below approach is both safe and effective and the immediate and long-term advantages of a single-stage approach justify its utility in this select group of patients.

Can radiation induce pituitary tumors? Giant prolactinoma after radiation exposure

Radiation is a well-known etiology for many CNS tumors, including meningiomas, sarcomas and gliomas. However, occurrence of pituitary adenoma after radiation exposure is rare. We report a 21-year-old man with a pituitary adenoma, who was treated with post-operative radiotherapy for pontine glioma at 6 years of age. The role of radiation exposure in the etiology of pituitary adenoma is discussed, along with a literature review of radiation-induced tumors.

Prolactinoma and estrogens: pregnancy, contraception and hormonal replacement therapy

The stimulatory role of estrogen on prolactin secretion and on proliferation of lactotropic cells is well established in terms of physiology but could this phenomenon be extended to include harmful effects of estrogens on prolactinoma? The aim of this review is to provide an up-to-date assessment of this subject with regard to pregnancy, use of contraceptive pills and postmenopausal hormone replacement therapy. Dopamine agonists allow women presenting prolactinoma to recover their ovulation cycles and become pregnant. There is no adverse data concerning the safety of dopamine agonists such as bromocriptine, if the woman is treated during the first trimester of pregnancy but there is little information regarding the most recent treatments such as cabergoline or quinagolide. In women with microadenomas, pregnancy generally has little impact on their adenoma, delivery is normal and breast-feeding is allowed. Concerning macroprolactinomas, tumor progression during pregnancy is possible and endocrine follow-up remains necessary. Contraceptive pills containing estrogen and progestins are currently the best-tolerated and the most effective contraception. This type of contraceptive has long been avoided in patients presenting prolactinoma. While the literature has little to say on this subject and provides no adverse information, professional experience suggests that this attitude should be amended and that women presenting microprolactinoma should be allowed to use current contraceptive pills (containing 30 microg or less of ethinyl estradiol). The most important problem to overcome with this type of prescription, which masks the clinical consequences of hyperprolactinemia, is the possibility of overlooking hypophyseal disease that could result from this approach. The problem of macroprolactinoma is different; the possibility of prescribing contraceptive pills must be evaluated on a case-by-case basis and the impact of the drug on the adenoma must be very closely monitored. Estrogen replacement therapy in patients presenting hypogonadism should be attempted in patients with a history of prolactinoma and standard-monitoring precautions should be taken. In menopausal women, when replacement therapy is desirable, the presence of a microprolactinoma should not by itself avoid this prescription.

Development of a macroprolactinoma in association with hormone replacement therapy in a perimenopausal woman with presumed idiopathic hyperprolactinemia

OBJECTIVE

To describe a 48-year-old woman with presumed idiopathic hyperprolactinemia, who was found to have a macroprolactinoma after receiving hormone replacement therapy for almost 3 years.

METHODS

We present a detailed case report, including a chronologic summary of clinical and laboratory findings as well as the drug history of our patient. The related literature is also reviewed.

RESULTS

Premenopausal women with idiopathic hyperprolactinemia or microprolactinomas (<1 cm) are treated with dopamine agonists if fertility is desired or galactorrhea is bothersome. Otherwise, estrogens and progestational agents may be prescribed to regularize menses and prevent osteoporosis. Several case reports of prolactinoma formation or enlargement after exposure to exogenous estrogens have been published. In our patient, a perimenopausal woman with presumably idiopathic long-standing hyperprolactinemia, a macroprolactinoma developed within 3 years after initiation of hormone replacement therapy for management of perimenopausal symptoms. The only clue for ordering a pituitary imaging study in this case was a substantial increase in the level of the serum prolactin. Treatment with cabergoline normalized the patient's serum prolactin level and considerably decreased the size of her pituitary adenoma.

CONCLUSION

It is postulated that exogenous estrogens could have an important role in tumor development or growth in some patients with idiopathic hyperprolactinemia. Therefore, it is recommended that women with idiopathic hyperprolactinemia or microprolactinomas treated with estrogens be considered for concomitant therapy with dopamine agonists. In all cases, serum prolactin levels should be diligently monitored.

Pathogenesis of prolactinomas

In recent years the demonstration that human pituitary adenomas are monoclonal in origin provides further evidence that pituitary neoplasia arise from the replication of a single mutated cell in which growth advantage results from either activation of proto-oncogenes or inactivation of tumor suppressor genes. However, with the exception of one RAS mutation identified in a single unusually aggressive prolactinoma resistant to dopaminergic inhibition that resulted to be lethal, no mutational changes have been so far detected in prolactinomas. In the absence of genetic changes, modifications in the level of expression of oncogenes or tumor suppressor genes have been detected in these tumors, although it is unknown whether these changes have a causative role or are a secondary event. Indeed, our knowledge on the molecular events involved in lactotroph proliferation is even more limited in comparison to the other tumor types, since these tumors are very infrequently surgically removed and therefore available for molecular biology studies. In this respect, it is worth noting that the molecular and biological abnormalities so far described in prolactinomas mainly concern aggressive and atypical tumors and likely do not apply to the typical prolactinomas, that are characterized by good response to medical treatment and a very low growth rate.

Resolution of macroprolactinoma-induced symptomatic hydrocephalus following cabergoline therapy

A 71-year-old man was referred because of memory loss. Magnetic resonance imaging showed a pituitary macroadenoma associated with hydrocephalus. Marked hyperprolactinaemia was present. After 2 months of cabergoline therapy, magnetic resonance imaging showed tumour shrinkage with resolution of the hydrocephalus. We report, for the first time, the adequate and rapid clinical response of a macroprolactinoma-induced symptomatic hydrocephalus in an elderly man to a low and once-a-week dose of cabergoline therapy. Medical therapy with this dopamine agonist in this particular patient was so effective that ventriculo-peritoneal shunting could be avoided.

Prolactinoma with a high adrenocorticotropic hormone level caused by meningitis--case report

A 69-year-old man was admitted semicomatose with high-grade fever and meningeal signs. Magnetic resonance imaging showed a supra- and intrasellar lesion. Hormone studies on admission showed increased serum prolactin, adrenocorticotropic hormone (ACTH), and cortisol titers. However, the serum ACTH and cortisol levels returned to normal after treatment of meningitis with an antimicrobial agent. The histological diagnosis was pituitary adenoma. Immunohistological staining showed positive reaction for prolactin but not for ACTH. This is a rare case of prolactinoma with a high serum ACTH level caused by meningitis.

TSPY-LTA transgenic mice develop endocrine tumors of the pituitary and adrenal gland

In an attempt to determine the susceptibility of spermatogonia to malignant transformation transgenic mice were generated harboring a 1.3 kb 5'-flanking region of the germ cell specific expressed human testis specific protein, Y-encoded gene fused with the simian virus 40 large T antigen (TAg). Unexpectedly, TAg expression in transgenic mice was also detected in somatic tissues. Between days 65 and 85 after birth most of the transgenic mice developed anterior lobe tumors of the pituitary gland and to a less extent medulla type tumors of the adrenal gland. In addition, a few older transgenic mice developed tumors of the seminal vesicle, but no testicular tumors were observed in transgenic mice up to an age of 5 months. The pituitary tumors were immunoreactive for anti-prolactin (PRL) and anti-adrenocorticotropic hormone (ACTH). PRL and corticosterone concentrations in serum of transgenic mice were significantly increased. Taken together, our studies provide a novel mouse model for pituitary adenomas displaying a unique combination of hormone expression by tumor cells secreting PRL and ACTH.

Prolactinoma and other head and neck tumors after scalp irradiation

Tumors of the thyroid and parathyroid glands may develop together or separately in patients who previously have been exposed to head and neck irradiation. Whether cranial irradiation confers an increased risk for pituitary adenoma remains unknown. We report the case of a 52-year-old woman who was treated during childhood for tinea capitis with scalp irradiation and later in life developed a prolactin-secreting tumor, a parathyroid adenoma, a benign thyroid lesion, and a basal cell carcinoma of the skin. She was treated successfully with bromocriptine and surgical removal of the parathyroid adenoma. Molecular analysis of the parathyroid tissue failed to demonstrate any abnormality of the multiple endocrine neoplasia Type 1 gene. This case report is the first to describe a prolactin-secreting tumor that developed in association with other endocrine neoplasia after head and neck irradiation. Our case suggests that multiple endocrine neoplasia may develop in a sporadic pattern after scalp irradiation.

Ovarian dependence for pituitary tumorigenesis in D2 dopamine receptor-deficient mice

Hypophyseotropic dopamine exerts a tonic inhibitory tone on pituitary lactotrophs by the activation of dopamine D2 receptors (D2R). Ablation of D2R through gene knock-out approaches results in hyperprolactinemia and prolactinomas. This phenotype is more severe and develops more rapidly in female mice. We tested whether the female hypersensitivity is due solely to the loss of D2R inhibitory tone or concomitant stimulation by ovarian factors. C57BL/6J congenic D2R(-/-) mice were ovariectomized at 2 months of age and serum PRL levels were measured serially. Ovariectomy attenuated hyperprolactinemia and after 18 months, D2R(-/-) mice had average pituitary weights of 4 mg, compared with 60 mg in the intact group. 17beta-Estradiol did not restore PRL secretion or pituitary weight. Although the pharmacologic dose of estradiol slightly increased pituitary weight in wild-type and D2R(-/-) mice, it inhibited serum PRL in both intact and ovariectomized females and in castrated males. For comparison, we tested the estradiol response of wild-type 129S6/SvEv mice in the same paradigm and found the expected increase in pituitary weight and serum PRL. Our results demonstrate that the development of hyperprolactinemia and prolactinomas in mice lacking D2R is dependent on ovarian stimulation and likely involves a factor(s) in addition to estrogen. Furthermore, we showed that estradiol-induced proliferation and PRL secretion can be differentially regulated in a strain-specific manner. These findings illustrate the importance of genetic background when analyzing endocrine regulation in mutant mouse models.

Lack of prolactin receptor signaling in mice results in lactotroph proliferation and prolactinomas by dopamine-dependent and -independent mechanisms

Hypothalamic dopamine inhibits pituitary prolactin secretion and proliferation of prolactin-producing lactotroph cells by activating lactotroph dopamine D2 receptors (D2Rs). Conversely, prolactin (PRL) stimulates hypothalamic dopamine neurons via PRL receptors (PRLRs) in a short-loop feedback circuit. We used Drd2(-/-) and Prlr(-/-) mutant mice to bypass this feedback and investigate possible dopamine-independent effects of PRL on lactotroph function. The absence of either receptor induced hyperprolactinemia and large prolactinomas in females. Small macroadenomas developed in aged Prlr(-/-) males, but only microscopic adenomas were found in Drd2(-/-) male mice. Pharmacologic studies in Prlr(-/-) mice with D2R agonists and antagonists demonstrated a significant loss of endogenous dopamine tone, i.e., constitutive inhibitory signaling by the D2R, in the pituitary. However, Prlr(-/-) mice exhibited more profound hyperprolactinemia and larger tumors than did age-matched Drd2(-/-) mice, and there were additive effects in compound homozygous mutant male mice. In vitro, PRL treatment markedly inhibited the proliferation of wild-type female and male Drd2(-/-) lactotrophs, but had no effect on female Drd2(-/-) lactotrophs, suggesting a downregulation or desensitization of PRLR in response to chronic hyperprolactinemia. We conclude that PRL inhibits lactotrophs by two distinct mechanisms: (a) indirectly by activation of hypothalamic dopamine neurons and (b) directly within the pituitary in a dopamine-independent fashion.

From prolactin cell to prolactinoma

The pathogenesis, diagnosis and treatment of common pituitary neoplasms is based on the understanding of the differentiated hormone expression by specific pituitary cell types and of the central hypothalamic, peripheral and local control of their hormonal secretion (endocrine, autocrine, paracrine regulation). Tumorigenesis is the result of a complex multistep process. It is likely that a molecular genetic alteration initially leads to cell transformation. Nevertheless the transformed cell is dependent on hormonal and/or growth factor stimulation for tumor progression. This cascade is responsible for autonomic hormone secretion, and cell proliferation. PRL cells do not behave identically in terms of cell function. Functional diversity among PRL cells is documented in vitro, in terms of basal and synthetic capacity and in respect to responsiveness to dopamine and oestrogen regulation. These in vitro observations can be extended to the in vivo situation. In the intact pituitary, PRL cells differ in their relative content of PRL and their response to secretagogues. These differences relate to their topographical localization within the pituitary. Prolactinoma are mainly composed of cells with a high basal synthetic and secretory capacity and arise preferentially in the peripheral parts of the hypophysis. It is therefore tempting to postulate that the "in situ milieu" within the pituitary is relevant for the development of prolactinoma. By stimulating growth in certain areas, there is an increased probability of mutation. At the same time growth of a mutated PRL cell could be stimulated.

Transforming growth factor-beta regulation of estradiol-induced prolactinomas

Prolactin-secreting adenomas (prolactinomas) are the most prevalent form of pituitary tumors in humans, and increased tumor growth under estrogenic influence in female patients is often of clinical concern. Extensive experimental work has uncovered the roles of estrogen receptors and various growth-regulatory peptides in estradiol action on lactotropes. However, it is only recently that we are beginning to gain insight into how these growth factors interact to regulate estradiol action on lactotrope cell proliferation. Recent studies have identified the regulatory role of TGF-beta-related peptides in estradiol action on lactotropes. Additionally, these studies determined that TGF-beta and FGF interact to facilitate the communication between lactotropes and folliculostellate cells that is necessary for the mitogenic action of estradiol. This review addresses the role of estradiol in prolactinoma formation and summarizes data that support a novel concept: Alterations in the expression and action of TGF-beta isoforms are crucial steps in estradiol-induced tumorigenesis.

Role of estrogen in alcohol promotion of breast cancer and prolactinomas

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chair was Dipak K. Sarkar. The presentations were (1) Dual role of estrogen as hormone and carcinogen in mammary carcinogenesis, by Joachim G. Liehr; (2) Alcohol and breast cancer: Studies using animals, by Keith W. Singletary; and (3) Evaluation of the role of estrogen in mediation of ethanol effect on prolactinoma: Studies using animals, by Dipak K. Sarkar.

[Neurosurgery and pituitary tumors: etio-pathogenic considerations]

PITUITARY ADENOMA: Based on the experience of nearly 5000 cases of surgically treated pituitary tumors at the neurosurgery department of the Foch Hospital, the pituitary adenoma is the most frequent pituitary tumor. Secreting tumors lead to a clinical syndrome depending on the level of hormone overproduction. Gonadotrop or non-functioning pituitary adenomas are mainly macroadenomas presenting with visual symptoms, hypopituitarism or as an incidentaloma. Anatomical features dictate the surgical approach. OTHER TUMORS: The other types of hypophyseal tumors, such as craniopharyngioma, Rathke's cleft cyst or others are usually surgical tumors because medical treatment is ineffective. Malignant pituitary tumors are unusual.

[Experimental investigation on the etiology and pathogenesis of pituitary prolactin-secreting tumor]

Male SD rats transplanted with an extra pituitary in the renal capsule and treated chronically with 17-beta-estradiol (E2) were used in the studies on the pathogenesis and the underlying mechanisms of pituitary prolactin-secreting tumor (prolactinoma). The results indicated that after long treatment with E2, prolactin-secreting tumor was generated in both eutopic and ectopic pituitary, accompanied by hyperprolactinemia and overexpression of PRL gene. No apparent difference was observed in histology and ultrastructure between them. Further investigations showed that some growth factors might be involved in the tumorigenesis of prolactinoma in vivo and in vitro. A point mutation was found in the proximal promoter of PRL gene only in eutopic prolactinoma by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP), suggesting that the base change in the promoter may be related to the overexpression of PRL gene. This hypothesis has been confirmed by the increased activity of luciferase reporter fused to the mutant promoter in vitro. The coincidence of overexpression of PRL, TGF alpha and TGF beta 1 gene, and the point mutation detected in eutopic pituitary prolactinoma suggested that neuro-endocrine-immune interactions in vivo might be associated with pituitary prolactinoma formation. The mechanisms mediating tumorigenesis of eutopic and ectopic prolactinoma, respectively, may be different.

Pituitary prolactin-secreting tumor formation: recent developments

Prolactinoma is the most common type of primary pituitary tumors. It occurs more frequently in women than in men. Dopaminergic agonists are effective in the shrinkage of prolactin-secreting pituitary tumor and are preferred in some patients. However, pituitary radiotherapy may enable the long-term removal of prolactin-secreting tumor cells. Recent evidence suggests that prolactinoma is a heterogeneous disorder with complicated and multifactorial etiology and pathogenesis. Apparently, a thorough understanding of prolactinoma tumorigenesis would be important. To facilitate investigations on tumorigenesis of prolactinoma, animal models for prolactinomas have been developed. These models have expedited our progress in the recent years. Many researchers consider the F(344) rat to be the most sensitive strain of rats to estrogen (E(2))-induced prolactinoma formation. Nonetheless, E(2) treatment for 60 days also induces the formation of pituitary prolactin-secreting adenoma in male Sprague-Dawley (SD) rats. Evidently, the SD rat is also a good animal for prolactinoma investigations. Following E(2) implantation, prolactinomas developed in the eutopic adenohypophysis in situ and/or ectopic pituitary grafted under the renal capsule in SD rats. These observations favor the hypothesis that prolactinoma growth is the result of pathological changes in the adenohypophysis and/or hypothalamus. In the latter case, abnormal release of hypothalamic dopamine, GABA, or brain-gut peptides (such as cholecystokinin, vasoactive intestinal polypeptide, galanin, angiotensin, opioid peptide, gastrin, gastrin-releasing peptide, pancreatic polypeptide, and adrenocorticotropic hormone) results in some of the pathological changes that may lead to hyperprolactinemia and/or prolactinoma development. Dysregulation of prolactin synthesis and secretion may be the result of prolactin gene modulation. In E(2)-induced rat prolactinomas, prolactin mRNA contents and the expression of some proto-oncogenes, e.g. c-myc and c-ras, TGFalpha and TGFbeta1 mRNA were significantly changed. The above findings are consistent with results in human prolactinoma development. In addition, in rats abnormal expression of the prolactin gene was correlated with hypomethylated status of CpG sites in exons 1, 2 and 4 of the prolactin gene, as well as the increase in hypersensitive sites to DNase 1 in the encoding region of the prolactin gene. In E(2)-treated rats, a point mutation with a base substitution from cytidine (C) to adenine (A) was found at the -36-bp site of the proximal promoter of the prolactin gene in eutopic pituitary prolactinomas, but no change was observed in the same sequence of the prolactin gene in ectopic prolactinoma. The association of a base substitution with the hyperexpression of the prolactin gene in eutopic prolactinomas suggests that different mechanisms may mediate the formation of eutopic and ectopic prolactin-secreting tumors. Melatonin decreases the expression of the prolactin gene in vitro suggesting that this pineal hormone may be a potential anticarcinogen in vivo. It has also been shown that MT(2) (Mel(1b)) melatonin receptors are expressed in anterior pituitary cells. The use of melatonin as a preventive or therapeutic drug for prolactinomas should be further investigated. In summary, improved knowledge on tumorigenesis of prolactinomas, especially in the rat model, was noted. These E(2)-induced rat prolactinoma models would facilitate future investigations, and expected results shall be fruitful and exciting for the development of future drug designs for the prevention and/or treatment of prolactin-secreting pituitary tumors.

Pituitary tumor registry: a novel clinical resource

Pituitary adenomas result in clinical sequelae and accelerated mortality due to central mass effects or pituitary hormone hypersecretion and/or insufficiency. The low annual incidence and prolonged natural history of these rare tumors has hindered efforts to evaluate long-term clinical outcomes. Care of these patients is often provided by larger tertiary specialist referral centers. A novel evidence-based computerized pituitary tumor registry was developed to systematically evaluate epidemiological, biochemical, and clinical outcome data. Retrospective registration of 371 patients [99 clinically nonfunctioning tumors (CNFTs), 176 acromegalics, and 96 prolactinomas] with radiological, biochemical, and clinical evidence of pituitary tumors was performed. Analysis of this primarily specialist-referred population revealed a female predominance among CNFT (60%) and prolactinoma (69%) patients. Males had a significantly greater frequency of macroadenomas than females for CNFTs (92% vs. (68%) and for prolactinomas (74% vs. 40%). Males with prolactinomas also had higher mean pretreatment serum PRL levels (1206 vs. 219 ng/mL). Concurrent hyperprolactinemia was present in CNFT (47%) and acromegaly (33%) patients. Radiographic cure, defined as absence of visualized tumor, was achieved in 21% of CNFTs, 34% of acromegalies, and 21% of prolactinomas. Biochemical remission, defined by normalization of hormonal tumor markers, was observed in 35% of acromegaly and 39% of prolactinoma patients in the registry, thus reflecting the tertiary referral patterns. Nine premature deaths (patients aged < or =65 yr) occurred in the acromegaly subpopulation, whereas no premature deaths were encountered in nonacromegalic patients. In conclusion, this unique and comprehensive pituitary tumor registry enables identification of diagnostic and prognostic markers and evaluation of long-term clinical outcomes. Prospectively, this registry will improve therapeutic guidelines and cost-effective pituitary tumor management.

Pituitary lactotroph adenomas develop after prolonged lactotroph hyperplasia in dopamine D2 receptor-deficient mice

Tuberoinfundibular dopamine tonically inhibits PRL expression and secretion from the pituitary gland by the activation of dopamine D2 receptors (D2R) localized on lactotrophs. Mutant female mice that lack D2Rs have persistent hyperprolactinemia but also develop extensive hyperplasia of pituitary lactotrophs and peliosis of the adenohypophysis at 9 to 12 months of age, while age-matched male D2R-deficient mice have no morphologic adenohypophysial lesion. We now report that both female and male D2R-deficient mice 17 to 20 months of age develop pituitary lactotroph adenomas. Of 12 aged female mice examined, all developed monohormonal PRL-immunoreactive neoplasms that had a characteristic juxtanuclear Golgi pattern of PRL staining and loss of the reticulin fiber network. Several of these adenomas were 50-fold larger than normal glands with marked suprasellar extension and invasion of brain but no gross evidence of distant metastases. They also had striking peliosis that was more marked than the lesion seen in the hyperplastic pituitaries of the younger females. These findings demonstrate that a chronic loss of neurohormonal dopamine inhibition promotes the hyperplasia-neoplasia sequence in adenohypophysial lactotrophs. Our results are analogous to previous data indicating that protracted stimulation of adenohypophysial cells by hormones or growth factors results in proliferation with initial hyperplasia followed by the development of neoplasia. Six aged male D2R-deficient mice had slightly enlarged anterior pituitaries similar in size to normal female glands. However, each case exhibited multifocal, microscopic lactotroph adenomas with strong nuclear immunoreactivity for estrogen receptors and Pit-1 transcription factor. The unexpected development of adenomas in males without preexisting or concomitant hyperplasia suggests that prolonged loss of dopamine inhibition may also cause neoplasia by distinct cellular mechanisms in male and female animals.

Pituitary tumours in the elderly: a 20 year experience

The proportion of the elderly in the population is increasing, and the appreciation and management of medical problems in this age group will therefore become more important. We therefore decided to determine the clinical features and types of pituitary tumour presenting in the elderly, and to examine the treatment and outcome in this group. We conducted a retrospective case-note review from a specialist endocrine and neurosurgical unit in a tertiary referral centre. Eighty-four patients aged 65 years and over on diagnosis of a pituitary tumour were referred to the unit between 1975 and 1996. There were 45 males and 39 females, and the mean age was 72.4 years (range 65-86). Over half of the pituitary lesions were non-functioning adenomas (NFAs) (60.7%). GH-secreting tumours were present in 11 (13.1%) and macroprolactinomas in 7 (8.1%). Four patients had microadenomas and 17 had miscellaneous pituitary-related lesions. Visual deterioration was the commonest mode of presentation in 33 (39.3%), but 54 (64.3%) had evidence of visual impairment on detailed examination. Despite the majority of patients (80.8%) having coexisting medical conditions, trans-sphenoidal surgery was performed in 60 (71.4%) and was well tolerated with a zero peri- and post-operative mortality rate, and post-operative complications in 11 (13.1%). Pituitary tumours in the elderly are most frequently NFAs that present with visual deterioration and hypopituitarism. The fact that 46.5% were pan-hypopituitary on diagnosis and that 64.3% of patients had visual impairment suggests a delay in diagnosis in this age group. Despite significant coexisting medical pathology in this large series of patients, surgery was safe and successful in the majority.

Hormonal control of pituitary prolactin-secreting tumors

Prolactin secreting adenomas (prolactinomas) are the most prevalent form of pituitary tumors in humans. Prolactinomas have been linked to estrogen exposure in humans and animals. However, the mechanism by which estrogen increases mitogenesis in lactotropes, as well as other estrogen responsive cells, is not well understood. Given the complex nature of steroid hormones and their wide array of actions, it seems plausible that there are multiple ways in which estrogen can exert its cell-transforming actions. Estrogen has a wide range of actions on cells depending on the cell type, receptor levels, and other factors present in the cell. A defect at any point could play a potential role in cell transformation. The source of such defects could be the result of any of a wide range of possibilities, including genetic predisposition, prolonged exposure to sufficient levels of the steroid hormone, or other insults to the cell which lead to altered responsiveness to estrogen in some way. This review discusses the recent advances that have been made in the area of understanding estrogen action in transformation of pituitary lactotropes.

[E2-induced prolactin-secreting tumor of heteroplasty pituitary in renal capsule of the rats]

OBJECTIVE

A prolactin-producing tumor induced by 17-beta-estradiol (E2) in isotransplanted pituitaries under renal capsules of SD rats were studied.

METHODS

Male SD rats (30 days old) were transplanted with an isologaus pituitary under renal capsule and treated with subcutaneous implantation of an empty or E2-laden silastic capsule.

RESULTS

After treated with E2 for 60 days and 120 days, both the eutopic and ectopic pituitaries were more than three times heavier than those from control rats, accompanied by hyperprolactinemia, and the body weight of rats decreased significantly. The effects of E2 on the weight of eutopic pituitary and the concentration of plasma PRL were time-dependent. In situ hybridization was employed to measure the levels of PRL mRNA expression in cells from the eutopic and ectopic pituitaries 120 days after treatment of E2. The PRL mRNA contents in both the eutopic and ectopic pituitary cells were much greater than those in untreated pituitary cells. But PRL mRNA levels showed no significant difference between the eutopic and ectopic pituitary cells.

CONCLUSIONS

Our previous data has shown that prolactinomas can be induced by chronic treatment of E2 in eutopic pituitaries of SD rats. In present study it appeared that E2 exerted similar effect on the ectopic pituitaries which were distant from the hypothalamus. Our results also demonstrated that E2 could promote the PRL gene expression in both the eutopic and ectopic pituitary cells, and there was no significant difference between them. Our data suggested the possibility of PRL-producing pituitary tumors could originate from anterior pituitary.

Targeting of transforming growth factor-alpha expression to pituitary lactotrophs in transgenic mice results in selective lactotroph proliferation and adenomas

The PRL-secreting cells of the pituitary gland normally express transforming growth factor-alpha (TGF alpha). To determine the effect of increasing TGF alpha expression in the pituitary, a transgenic mouse model was created in which overexpression of human TGF alpha was directed to the pituitary lactotrophs using the rat PRL promoter. Of the four gene-positive mouse lines, two expressed the messenger RNA corresponding to the transgenic in the pituitary glands. However, in both these lines, expression could only be detected in the female animals. Expression of the transgenic could be detected as early as 1 month of age, but no pathology or developmental abnormalities were detected until the animals reached 6 months, at which time, hyperplasia of the lactotrophs. By the age of 12 months, all of the homozygous transgenic females had developed pituitary adenomas that were immunopositive for PRL. The other hormone-producing cells of the pituitary showed no obvious pathology. The male transgenics developed neither hyperplasia nor adenomas, nor did the gene-positive transgenic lines that did not express the transgene. In no case was an aggressive pituitary tumor seen. This transgenic mouse model indicates that TGF alpha overexpression by lactotrophs stimulates the growth of these pituitary cells. Furthermore, TGF alpha has a highly localized action in the pituitary gland, resulting only in lactotroph hyperplasia and prolactinomas. These observations suggest that TGF alpha might play a role in the development of prolactinomas.

[Prolactinoma after craniocerebral trauma]

A female patient, now twenty-four years old, suffered from a severe cerebral contusion in 1983 as a result of a car accident. At the time of the accident, she had a regular menstrual cycle. Since 1985, she has contracted oligomenorrhoea and since 1988 secondary amenorrhoea. In 1988, we diagnosed by CT-scan and NMR-imaging an excessive hyperprolactinaemia caused by a pituitary adenoma. Neither surgical intervention, nor conservative medication could reduce the prolactin level to normal. We suspect, that there is an association between the cranial injury and the appearance of the pituitary tumour.

Hormonal screening in impotent patients

Of a total 260 impotent patients entered in a hormonal study, serum testosterone, prolactin and hormonal abnormalities were detected in 30 (11.5%) patients (18 with hypotestosteronemia and 12 with hyperprolactinemia). The 18 cases of hypotestosteronemia included: 8 cases of hypergonadotropic hypogonadism due to klinefelter's syndrome (1), orchitis (2), chronic alcoholism (1), and idiopathic primary gonadal failure (4) and 10 cases etiologically unknown hypotestosteronemia. Nine of the 18 patients also displayed other organic etiologies (6 vasculogenic and 3 diabetic impotence). After replacement of testosterone propionate by intramuscular injection, the improvement in impotence was significant in 12 patients (excellent in 1, good in 11) and insignificant in 6 (poor in 3, no response in 3). The positive response rate was 89% (8/9) for sole hypotestosteronemia and 44% (4/9) for hypotestosteronemia accompanied by other organic causes of impotence. In the 12 patients with hyperprolactinemia, 4 had prolactinomas. Of these, 3 were treated by surgery and 1 with bromocriptine. Three (excellent in 2, good in 1) of the 4 showed a positive erection response afterwards, but the other patient's response was poor because of postoperative residual tumor. Two patients had drug-induced hyperprolactinemia (haloperidol and methyldopa) and for one, impotence was improved after withdrawal of haloperidol. However, the other responded poorly due to vasculogenic impotence. Six patients with hyperprolactinemia of unknown etiology (2 accompanied by vasculogenic impotence, 2 by diabetic impotence and 2 by sole hyperprolactinemia) were treated with bromocriptine and improvement was noted in 3. The positive response rate was 71.4% (5/7) for sole hyperprolactinemia and 40% (2/5) for hyperprolactinemia accompanied by other organic causes of impotence. Good results were achieved in prolactinoma, sole hyperprolactinemia and hypotestosteronemia.(ABSTRACT TRUNCATED AT 250 WORDS)