Clinical and endocrine features of hyperprolactinaemic amenorrhoea

Cerebrospinal Fluid Rhinorrhoea in Pituitary Tumours

Three cases of CSF rhinorrhoea due to pituitary tumours are reported and the literature reviewed. The treatment of choice appears to be trans-sphenoidal exploration of the pituitary fossa with insertion of a free muscle graft followed by radiotherapy. The probability of the tumour being a prolactin-secreting adenoma is discussed.

A novel mouse model of hypogonadotrophic hypogonadism: N-ethyl-N-nitrosourea-induced gonadotropin-releasing hormone receptor gene mutation

An autosomal-recessive mutation that causes hypogonadotrophic hypogonadism was isolated during an N-ethyl-N-nitrosourea mutagenesis screen in mice. Affected males had micropenis and small, undescended testes with spermatogenesis arrested at the pachytene stage of meiosis, leading to sterility. Androgen-sensitive organs were small and immature. Affected females were externally normal but sterile with small ovaries due to an arrest at the secondary stage of folliculogenesis, and the uterus and oviducts were thin and immature. Circulating reproductive hormones were significantly decreased in affected males and females. There was also a dramatic reduction in the numbers of FSH- and LH-producing gonadotrophs. Meiotic mapping of the mutation and candidate gene sequencing determined that the N-ethyl-N-nitrosourea-induced lesion is in the third transmembrane domain of the GnRH receptor gene (Gnrhr). In vitro studies indicate that the mutant receptor is not coupled to the plasma membrane signal transduction system. Moreover, this mutant cannot be rescued with defined GnRH receptor pharmacoperones (pharmacological chaperones), an approach that rescues many other misfolded mutants. The mutant GnRH receptor was also shown to exert a dominant-negative effect on wild-type receptor function, indicating that the mutant receptor is unable to fold properly and likely misrouted within the cell, not reaching the plasma membrane. Surprisingly, Gnrhr mutant transcripts were significantly up-regulated in the pituitaries of Gnrhr mutants, revealing a previously unknown autoregulatory feedback loop. This is the first report of a mouse with a Gnrhr loss of function mutation. These GnRH-insensitive mice provide a novel animal model for the study of human idiopathic hypogonadotrophic hypogonadism.

Contemporary management of prolactinomas

Prolactin-secreting pituitary adenomas--prolactinomas--are the most common type of functional pituitary tumor. Treatment of hyperprolactinemia is indicated because of the consequences of infertility, gonadal dysfunction, and osteoporosis. Making the correct diagnosis is important because the first line of therapy is medical management with dopamine agonists. Medical therapy is effective in normalizing prolactin levels in more than 90% of patients, but longterm treatment may be required in some patients. Transsphenoidal surgery is usually indicated in those patients in whom medical therapy fails or cannot be tolerated, or in patients who harbor microprolactinomas. In experienced hands, a hormonal and oncological cure can be achieved in more than 90% of patients after transsphenoidal removal of microprolactinomas with minimal risks. Thus, surgery may be an option for microprolactinomas in a young patient who desires restoration of fertility and avoidance of long-term medical therapy. The authors review the diagnosis and management of prolactinomas, including medical therapy, surgical therapy, and stereotactic radiosurgery.

Role of transient hyperprolactinemia in the late follicular phase of the gonadotropin-stimulated cycle

Background: Serum prolactin (PRL) concentration is known to transiently increase in rats; however, its change is obscure and the role of it is also unclear in women. We studied the relationship between estradiol (E2) and PRL production and the role of transient hyperprolactinemia in the late follicular phase of the gonadotropin-stimulated cycle. Methods: (1) Serum E2 and PRL concentrations were measured on an early follicular day and immediately before a human chorionic gonadotropin (hCG) injection in 60 patients with normoprolactinemia. Twelve of the 60 patients also received a gonadotropin injection with bromocriptine, and serum hormone levels were compared with those without bromocriptine. (2) Preovulatory serum E2 and PRL concentrations were compared between the natural and clomiphene treatment cycles in 14 hormonally normal women. (3) Changes of serum PRL concentrations were measured before and after E2 loading in five premature ovarian failure (POF) patients. (4) The E2 production by granulosa cells in the presence of PRL was measured. Results and Conclusion: Serum E2 and PRL concentrations were significantly increased by the gonadotropin injection. Bromocriptine treatment completely inhibited the PRL increase, but further increased serum E2 concentration on the late follicular day. The E2 loading increased serum PRL levels in POF patients. The clomiphene treatment increased serum E2 but decreased PRL concentrations. Prolactin significantly decreased E2 production by granulosa cells. A feedback loop may exist between E2 and PRL to control the excess E2 production induced by gonadotropin injection. (Reprod Med Biol 2002; 1: 69-74).

Expression of the steroidogenic acute regulatory protein and luteinizing hormone receptor and their regulation by tumor necrosis factor alpha in rat corpora lutea

Expression of both mRNA and protein of the steroidogenic acute regulatory protein (StAR), in correlation with progesterone (P) production and LH receptor (LHR) mRNA expression, was studied in the corpora lutea (CL) of gonadotropin-induced-pseudopregnant and pregnant rats at various stages of CL development. Immature female rats, 21-22 days old, were injected s.c. with 20 IU eCG to stimulate follicle growth and then with 20 IU hCG 48 h later to induce ovulation. The ovaries were removed at various stages of CL development; either CL were isolated and snap frozen for total RNA analysis, or whole ovaries were fixed in Bouin's fluid for paraffin sectioning. The results of in situ hybridization, immunohistochemistry, and Northern blotting showed that the increase in StAR mRNA and protein expression was well correlated with the increase in serum P concentration. StAR expression was restricted to the luteal cells or theca cells in antral follicles. Both StAR mRNA and protein in the CL of pseudopregnant rats increased steadily on Day 1 and Day 4, reached highest levels on Day 4, and then dropped sharply on Day 8 when luteolysis takes place. LHR mRNA content was high on Day 1 but dropped significantly on Day 2. LHR mRNA increased to high levels on Day 4 and 8 and then declined on Day 12. StAR mRNA and protein levels in the CL of pregnant rats were high during early luteal development (Day 2, 4), increased even further on Day 9, and decreased on Day 13 when luteolysis takes place. It is therefore suggested that the expression of StAR coincides well with the capacity of P production in the CL and that StAR expression can be used as a functional "marker" of CL development. To study the possible effect of cytokines on StAR expression, pseudopregnant rats on Day 5 were injected s.c. with 10 IU hCG plus 20 microg prolactin (PRL), with or without 500 IU tumor necrosis factor alpha (TNFalpha) 30 min later. TNFalpha significantly inhibited hCG/PRL-induced StAR and LHR mRNA expression at 1 and 3 h post-TNFalpha. It is suggested that the luteolytic effect of TNFalpha may be mediated by its direct inhibition on StAR expression or by an indirect decrease in LHR expression.

Plasma levels of parathyroid hormone-related peptide are elevated in hyperprolactinemia and correlated to bone density status

Osteopenia is an important clinical manifestation of hyperprolactinemia. Bone loss in these patients has mainly been attributed to concomitant deficiency of gonadal hormones rather than to hyperprolactinemia per se. Parathyroid hormone-related peptide (PTHrP) is expressed in human mammary tissue, and elevated circulating PTHrP levels as well as concomitant hypercalcemia have been described during lactation. We sought to determine circulating PTHrP levels in patients with long-standing hyperprolactinemia and whether PTHrP may exert possible systemic effects on bone and mineral metabolism. We studied 45 patients (30 women and 15 men) with persisting hyperprolactinemia 6 +/- 4 years (mean +/- SD) after trans-sphenoidal surgery for prolactin-producing pituitary adenomas. PTHrP levels in 117 healthy controls were 10.6 +/- 7.3 pmol-eq/l (mean +/- SD). In hyperprolactinemic patients, plasma PTHrP was elevated to 30.3 +/- 13.4 pmol-eq/l (p < 0.001, n = 45), and in patients with humoral hypercalcemia of malignancy PTHrP levels were 52.9 +/- 29.6 (p < 0.001 to controls and hyperprolactinemic patients). Fifty-three percent of hyperprolactinemic patients (n = 24) had clearly elevated PTHrP levels (> 2 SD). Retrospective immunocytochemical studies of the removed pituitary adenomas from 19 patients generally showed a higher degree of immunoreactivity for PTHrP (1-34) in all but one case when compared with normal pituitary tissue. Patients with elevated circulating PTHrP levels showed in most instances strong immunoreactivity to PTHrP in 70-100% of tumor cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amenorrhea during the reproductive years--is it safe?

OBJECTIVE

To collate information relating specifically to amenorrhea of different etiologies in young women, the long- and short-term implications of these states, and the optimal therapeutic strategy to treat these conditions.

DATA IDENTIFICATION

Studies related to these topics were identified through literature and Medline searches.

STUDY SELECTION

Those studies that relate specifically to amenorrhea in women of reproductive age, including etiology, diagnosis, and the implications of replacement therapy or nontreatment of this state, were selected.

RESULTS

Amenorrhea, as defined by the absence of menses for > or = 6 months, may be found in up to 3% of women in the reproductive years. Classification of amenorrhea involves defining the exact cause for the cessation of menses, be it hypothalamic, pituitary, ovarian, or lower genital tract in origin. The majority of amenorrheic young women have very low levels of estrogens, and a minority will have subnormal noncyclic estrogen levels, unopposed by P, due to anovulation. This distinction is important in considering the long-term implications of amenorrhea. Hypoestrogenic amenorrhea is associated with a significant loss of bone mineral density and the associated risk of osteoporosis and fractures. Lipoprotein profiles are also adversely affected, and this is associated with an increased risk of cardiovascular events. Anovulatory amenorrhea due to "unopposed" estrogen is associated with an increased risk of endometrial hyperplasia and endometrial carcinoma even in young patients. Therapy should be aimed at treating the underlying cause of amenorrhea, if possible, or reconstitution of an estrogen-P biphasic monthly cycle if not.

CONCLUSIONS

Untreated amenorrhea is associated with significant long-term morbidity, especially in young women. Early recognition and institution of treatment will minimize late complications.

Induction of ovulation with pulsatile GnRH

The use of pulsatile GnRH to treat infertile women who do not ovulate has been shown to be safe, simple, and effective and the preferred method of inducing ovulation in appropriately selected patients who are resistant to treatment with clomiphene citrate. Treatment with GnRH is particularly effective for restoring ovulation in patients with idiopathic hypogonadotrophic hypogonadism and partially recovered weight-related amenorrhoea, but less successful in patients with polycystic ovary syndrome and organic hypothalamic pituitary disease. Based on personal experience, we advocate routine use of the subcutaneous route, using 15 micrograms per pulse every 90 min, and we monitor the patient's progress by serial ultrasound scanning and measurement of serum gonadotrophin and oestradiol concentrations. If the patient does not respond we recommend adding treatment with clomiphene citrate (Homburg et al, 1988b). Treatment with intravenous GnRH is reserved for women who do not respond to the above combination of drugs. We do not treat patients with GnRH until their body mass index is in the normal range (between 20-25) and we avoid GnRH treatment in patients with hypersecretion of LH during the follicular phase. If LH concentrations are raised, an alternative method of treatment is recommended, such as ovarian diathermy (Armar et al, 1990). Finally, the question of whether GnRH deficiency in patients with hypogonadotrophic hypogonadism is caused by a specific genetic lesion is not yet fully resolved. Yang-Feng et al (1986) used a cDNA clone encoding the human GnRH precursor molecule in order to assign the GnRH gene to a particular human chromosome. They found a single site for GnRH sequences in the human genome and that the gene coding for GnRH is located on the short arm of chromosome 8. Experiments in the congenitally hypogonadal mouse have shown that it is possible to restore gonadal development and gametogenesis by gene transfer (Mason et al, 1987). Clearly an abnormality at the level of the genome may be responsible for the secretory defect in patients with hypogonadotrophic hypogonadism, but it has yet to be defined (Weiss et al, 1989). Presumably elucidation awaits the development of more refined methods because both the genetics and the clinical associations of GnRH deficiency are most persuasive. Meanwhile replacement treatment with GnRH provides a simple and safe form of treatment for managing the clinical syndromes of GnRH deficiency.

Heterogeneity of the polycystic ovary syndrome: clinical, endocrine and ultrasound features in 556 patients

This paper reports an analysis of the clinical, endocrine and ultrasound data within a population of 556 patients with ultrasound-diagnosed polycystic ovaries. Compared with those not so affected, hirsutism was associated with a higher mean serum testosterone concentration, infertility was associated with higher mean gonadotrophin concentrations, obesity was associated with a higher mean serum testosterone concentration, hyperprolactinaemia was associated with a lower mean serum testosterone concentration and smaller ovaries, alopecia was associated with lower mean serum LH and testosterone concentrations, and acanthosis nigricans was associated with obesity and a raised mean serum testosterone concentration. The heterogeneity illustrates the limitations in the use of specific clinical or endocrine criteria as requirements for the diagnosis of the polycystic ovary syndrome.

Effect of pituitary graft-induced hyperprolactinemia on adrenal circadian rhythmicity

Prolactin is involved in the regulation of several endocrine functions. In this study, the possible influence of hyperprolactinemia on circadian corticosterone secretion has been investigated. Pituitary grafted male and female rats exhibited increased plasma PRL levels at 1000 when compared to sham-operated controls. This increase was only maintained over the 24 h period in grafted female rats but not in males, thus suggesting a different sex dependent modification of the regulatory mechanisms of prolactin. The corticosterone secretion pattern in sham operated male and female rats was similar to those described earlier but was altered by hyperprolactinemia according to the sex of the animal. There was a significant decrease in the total amount of corticosterone secreted in a 24 h period in grafted males as compared to control animals, whereas no significant differences were observed in grafted female rats as compared to controls. Grafted females showed a 4 h delay in the 24 h secretion rhythm as compared to control animals. These data suggest that pituitary transplant induced hyperprolactinemia, directly or through modifications in catecholamine turnover, is able to modify adrenal rhythmicity.

Nyctohemeral rhythms of gonadal, thyroid and pineal function in the hyperprolactinemic male rat

In young adult male rats bearing a donor anterior pituitary gland grafted for 3 weeks under a kidney capsule, serum prolactin (PRL) concentrations were elevated and exhibited a rhythm with the highest values in the light phase. Serum PRL in control animals did not exhibit a significant rhythm. Eutopic pituitary PRL content, manifesting a biphasic (12-hr) rhythm with crests during the day and night in controls, exhibited a similar pattern in grafted rats though an overall reduction in pituitary PRL content was seen in the grafted animals. Neither the normal biphasic serum testosterone rhythm nor the normal 24-hr rhythm (nocturnal surge) of pineal N-acetyltransferase activity and melatonin content were altered in the hyperprolactinemic rats. Serum thyroxine (T4) and triiodothyronine (T3) and their free indices (FT4I, FT3I) and serum thyrotropin (TSH) were highest during the day in controls and grafted rats and a 12-hr rhythmic component was detected in data for these variables. In the grafted animals, the 12-hr component was reflected in an additional peak at night detectable by testing of means. The overall serum T4, FT4I, and TSH levels were lower in grafted rats though overall T3 and FT3I levels did not differ between grafted and controls. T3 uptake (T3U) values were similar between controls and grafted rats, in both cases exhibiting a fall during the night. Changes in serum thyronines could not be explained by changes in serum binding as assessed by the T3U, and thus may represent changes in thyroidal secretion of T4.(ABSTRACT TRUNCATED AT 250 WORDS)

Borderline hyperprolactinemia in infertile women: evaluation of the prolactin response to thyrotropin releasing hormone and double-blind placebo-controlled treatment with bromocriptine

Twenty-two women with on average more than 3 years unexplained infertility including normal menstrual cycles were studied because of borderline hyperprolactinemia (repeated serum prolactin concentrations 400-1000 mU/l). Randomized double-blind treatment with bromocriptine 5 mg daily (leading to adequate prolactin suppression) or matching placebo, each for 4 cycles, resulted in a cumulative rate after 4 months of 14.3 +/- 10.6% (SE) in both groups. Also, the results of treatment were not significantly related to the serum prolactin response to an intravenous injection of thyrotropin releasing hormone, whether the response was blunted (ratio of peak to basal prolactin within 60 minutes of injection no greater than 2), intermediate (greater than 2 to 4) or normal (greater than 4).

Epidemiology of infertility and polycystic ovarian disease: endocrinological and demographic studies

The frequency of polycystic ovarian disease (PCOD) as a cause of oligo-amenorrhea and infertility was determined, first by characterizing clinically occult PCOD using endocrinological methods, and secondly by estimating the frequency of overt and occult PCOD amongst infertile women residing in a particular area. Four groups of infertile women with oligo-amenorrhea due to 'functional' disorder were compared. The results show that by contrast with the groups having hyperprolactinemia or hypothalamic disorder the group with hirsutism (and therefore presumed PCOD) was closely resembled by a non-hirsute group in terms of estrogenization, LH level, LH/FSH ratio, prolactin level, body mass and responsiveness to clomiphene. The last group was therefore concluded to have a mild occult form of PCOD. The population studies revealed, first, that overt and occult PCOD accounted for 90% of patients with oligomenorrhea and 37% with amenorrhea, or 73% with oligo- or amenorrhea. Oligo- or amenorrhea accounted for 21% of couples with infertility and the annual incidence was 247 patients per million of the general population. The annual incidence of infertility due to PCOD per million was 41 with overt PCOD and 139 with occult PCOD (total 180). Of those, 140 appeared to respond well to clomiphene (78%) but 40 (22%) failed, requiring alternative therapy.

Prolactinoma presenting with intermittent third nerve palsy

A patient presented with a painful third nerve palsy. This resolved spontaneously, but recurred several months later. At his second presentation carotid angiography gave normal results, but a high resolution CT scan showed a tumour in the right parasellar region. The serum prolactin was raised at over 22,000 millimicrons/, showing this to be a prolactinoma.

Ovulation and normal luteal function during LHRH treatment of women with hyperprolactinaemic amenorrhoea

Five patients with hyperprolactinaemic amenorrhoea who had been resistant to, or intolerant of bromocriptine were treated with pulsatile LHRH therapy. Ovulation was induced in 9 of 12 treatment cycles. In one patient hyperstimulation occurred in the first cycle of treatment but subsequently she ovulated normally on a reduced dose of LHRH. The gonadotrophin and ovarian responses to treatment in ovulatory cycles were normal despite prolactin concentrations that remained elevated throughout treatment and rose still further with resumption of ovarian activity. The length of the luteal phase and the mid-luteal serum progesterone concentrations were also normal. Pulsatile secretion of progesterone in response to LHRH pulses were observed. These data show that ovulation and normal luteal function can be induced by physiological LHRH replacement in women with persistent hyperprolactinaemia. This confirms that the mechanism of anovulation in hyperprolactinaemic amenorrhoea is disordered LHRH secretion.

Pituitary localization of 3H-spiroperidol by an uptake/storage mechanism?

The lack of a pituitary imaging agent combined with the considerable clinical value for such an agent prompted an examination of 3H-spiroperidol (3HSp). Spiroperidol was selected for initial evaluation based on its high affinity for D2 receptors which are known to be present in the pituitary. A time course study of 3HSp concentration in rat pituitary and other tissues was conducted. Pituitary activity levels were found to be constant from 5 min to 4 h and were about 8 times levels in corpus striatum at 1 h. Blocking studies with (+) butaclamol and with unlabelled spiroperidol suggested the existence of both a D2 receptor mediated binding localization and a second uptake which is postulated to be an internalization process. Further studies involving ultracentrifugation of pituitary homogenates resulted in evidence for association of 3HSp with dense subcellular particles. 3HSp thus appears to be internalized by pituitary cells.

Use of DES-treated rats as an animal model for assessment of pituitary adenoma imaging agents

Prolactin (PRL) secreting pituitary adenomas are the most common type of pituitary tumors. An imaging agent which specifically localized in prolactinomas would be of considerable clinical value for both initial detection and also for monitoring the effects of dopamine agonist therapy. Tritiated spiroperidol (3HSp) was selected for initial evaluation as a possible imaging agent based on: demonstrated localization in the pituitary and demonstrated binding to human PRL-secreting tumor tissue. DES was implanted in Fischer F344 rats and induced prolactinoma formation was evidenced by increased pituitary weight, elevated serum PRL levels and by an increase in the proportion of PRL-secreting cells in the pituitary. 3HSp concentrations in pituitary and other tissues of DES-treated rats were assessed in female rats and correlation studies showed that a 5-fold increase in serum PRL was associated with a 6-fold increase in both pituitary weight and % dose/organ accumulation of 3HSp. The number of pituitary D2 receptors per mg of protein in tissue homogenates was similar in both normal and DES-treated females. A blocking study with (+)-butaclamol demonstrated a D2 receptor-mediated component to 3HSp localization. In summary, an animal model for prolactinoma was characterized. An assessment of 3HSp accumulation indicates that radiolabelled spiroperidol shows excellent potential for detecting PRL-secreting tumors of the pituitary.

Increased forearm bone mineral content after bromocriptine treatment in hyperprolactinemia

We studied 15 hyperprolactinemic women to evaluate possible modifications of bone mineral content after pharmacological treatment. Patients received a dopamine agonist (bromocriptine) for six months after which there was a significant decrease of prolactin plasma levels (P less than 0.01) and a significant increase of bone mineral content (P less than 0.05).

LH and FSH responses to GnRH in health and disease

LH and FSH responses to intravenous bolus GnRH were evaluated in healthy men and women and in patients with various hypothalmo-pituitary disorders. Higher LH FSH responses to GnRH were recorded. In prepubertal girls FSH responses were higher than those of LH; however, while FSH responses remained unaltered through pubertal development stages 2-5, there was a progressive increase in LH response during that period. GnRH test was marginally useful in diagnosis of delayed puberty but more so in hypogonadotropic hypogonadism and true precocious puberty. In experimental hyperprolactinemia, GnRH induced a near normal LH response but caused an exaggerated FSH response, which was normalized after clomiphene treatment. GnRH test was found to be useful to assess pituitary reserve of gonadotropins in a variety of clinical situations involving hypothalamo-pituitary gonadal axis.

The inability of dynamic tests of prolactin and TSH secretion to differentiate between tumorous and non-tumorous hyperprolactinemia

Certain hyperprolactinemic patients have an obvious pituitary tumor while others with normal pituitary radiology may or may not harbor a pituitary microadenoma. A variety of biochemical tests have been proposed to distinguish between those with and those without pituitary tumors. The aims of this study were: firstly to examine these tests to assess their efficacy in differentiating between patients with radiologically-demonstrated pituitary tumors and normal controls; and secondly to establish if those hyperprolactinemic patients with normal radiology formed two distinct groups biochemically as might be expected if some did and some did not have tumors. The prolactin (PRL) and thyroid stimulating hormone (TSH) response to domperidone and the PRL response to TRH and insulin-induced hypoglycemia have thus been examined in hyperprolactinemic subjects with and without radiological evidence of an adenoma and in normal controls. The basal serum PRL was similar in patients with and without radiological evidence of a pituitary adenoma. The serum PRL response to all stimuli studied, expressed as a percentage of initial values, was blunted in patients with known pituitary tumors with total separation from values in control subjects. Results for patients with normal pituitary radiology were similar to those for patients with tumors with minimal overlap with controls. The peak TSH increment after domperidone was exaggerated in patients with known tumors, but overlap with control values was observed in 25%. In patients with normal radiology the peak TSH increment after domperidone was similarly increased but again overlap with control values occurred in 28%. Cluster analysis showed no evidence of two subgroups of response with in the hyperprolactinemic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of long term administration of ovine prolactin on hypothalamic-pituitary testicular axis in rat

The effect of hyperprolactinaemia on testicular morphology and on hypothalamic-pituitary-testicular axis was studied in adult male Wistar rats. Animals received ovine prolactin (oPRL) 200 micrograms twice daily s.c.) for 24 and 36 days and were killed by exanguination. Blood was collected for hormonal determinations and sex accessory glands were removed for histological studies. Circulating testosterone (T) and luteinizing hormone (LH) levels showed a significant reduction after 36 days of treatment whereas plasma follicle-stimulating hormone (FSH) levels were unchanged in all animals. No macroscopic or light microscopic histological modifications were observed in the testes. The present results, while excluding a direct effect of hyperprolactinaemia on seminiferous tubules, suggest that LH suppression is the consequence of a central effect of the ovine PRL long-term administration. The increased DA turnover in the hypothalamus suggested as inhibitory on GnRH neurons could account for this effect. The reduction of T levels seems to be mediated by the LH suppression, even though a direct effect of oPRL on Leydig cell receptors could be hypothesized.

Reciprocal pattern of the TSH and PRL responses to dopamine receptor blockade in women with physiological or pathological hyperprolactinaemia

The TSH and PRL responses to administration of the two dopamine (DA) receptor antagonists sulpiride and domperidone, were studied in fifteen normoprolactinaemic subjects, twenty-two post-partum women and sixteen subjects with presumptive evidence of (six subjects) or surgically confirmed (ten subjects) prolactinomas. Sulpiride (100 mg i.m.) or domperidone (10 mg i.v.) elicited a slight increase in basal TSH levels in both normoprolactinaemic and post-partum women, but induced a clear-cut TSH rise in subjects with a tumour. Conversely, sulpiride and domperidone strikingly stimulated PRL secretion in normoprolactinaemic and post-partum women, but only slightly enhanced base-line PRL levels in women with prolactinomas. The reason for the reciprocal pattern of TSH and PRL responsiveness to DA receptor blockade of post-partum women and subjects with prolactinomas is presently obscure. Since baseline PRL levels in the two hyperprolactinaemic states overlapped widely, it would appear that hyperprolactinaemia per se is not responsible for such behaviour.

Human ovarian receptors to human prolactin: implications in infertility

In the human, hyperprolactinemia may interfere with fertility. To find out whether or not prolactin (PRL) can act directly on human ovarian tissues, in vitro studies involving specific binding of human PRL to various human ovarian elements were carried out. Human PRL was isolated from amniotic fluid, and its intact monomeric iodinated isohormone B was prepared. Labeled PRL was incubated with plasma membranes of either granulosa or whole follicular homogenates. Relatively high specific binding sites were obtained. Saturation studies and Scatchard analysis showed a single class of binding sites with high binding affinity (Kd = 1.8 x 10(8) M) and a concentration of 7.9 x 10(-15) moles/mg protein. These results clearly demonstrate the existence of specific receptors to isoprolactin B in ovarian elements with binding capacity and concentration at least equal to that found in other targets for PRL. It is reasonable to assume that hyperactivation of these receptors in states of hyperprolactinemia constitutes the cause for the disturbances in ovarian functions that lead to infertility.

Hypothalamic-pituitary function in myotonic dystrophy

Function of the hypothalamic-pituitary axis was investigated in seven patients with myotonic dystrophy (MD). HGH and ACTH secretion were normal. TSH response to TRH was impaired in about half the cases, without concomitant thyroid dysfunction. LH and FSH levels were often elevated, with inconsistent response to LH-RH stimulation, Gonadotrophin disturbances in MD have previously been attributed to a primary gonadal lesion, characteristically seen in this disease. High prolactin levels in six of our seven patients however suggest that gonadal failure may be also be due to hyperprolactinemia through the direct anti-gonadal effect of prolactin and its interference with hypothalamic-pituitary regulation of gonadotrophin secretion.

A practical approach to the investigation of the hyperprolactinaemic patient

Pituitary function was assessed in 39 patients with previously untreated hyperprolactinaemia. Primary hypothyroidism, drug-induced hyperprolactinaemia and chronic renal failure were excluded in all patients. All of the 22 patients (group 1), who had either a normal pituitary fossa or a minor radiological change on lateral skull X-ray, had completely normal pituitary function with the exception of 2 who were partially growth hormone-deficient. However, 9 of the 17 patients with macroadenomas (group 2) had a deficit of one or more anterior pituitary hormones. After the lateral skull X-ray 13 patients in group 1 had further neuroradiological investigations. In only one was a minor abnormality noted which had not been observed on the plain film and this was not of practical significance. In centres where hyperprolactinaemic patients with a normal pituitary fossa or a minor radiological change on lateral skull X-ray are treated with bromocriptine, further neuroradiological investigations and dynamic tests of pituitary function are not required.

Hypothalamic-pituitary-testicular function in men with PRL-secreting tumors

We studied the hypothalamic-pituitary-gonadal system in 33 men with PRL-secreting tumors to determine at which level(s) high PRL levels interfere with testicular function. In basal conditions serum PRL levels ranged between 24-4500 ng/ml, serum LH and FSH concentrations were lower than normal in 61% and 39% of patients; low testosterone (T) levels and sexual impotence appeared more common (85% and 88%) than that we expected on the basis of gonadotropin deficiency. Mean T increase after hCG in 14 patients with prolactinomas was significantly less than in normals (3.3 +/- 0.7) ng/Ml vs 7.3 +/- 0.5 ng/ml; p less than 0.025); a significantly higher T response to hCG was obtained in 5 cases retested after PRL levels had been reduced by therapy. GnRH test induced a normal LH rise in 45% of patients, Mean serum LH increase after clomiphene administration did not differ from that in normals, though 4 out of 10 patients showed an impared response. Metoclopramide injection did not cause a rise of LH in 11 patients so tested. These data, while not excluding a central influence of PRL on LHRH, suggest that in men the antigonadotropic effects of PRL are mainly exerted at the gonadal levels.

Gonadotropin secretion in rats bearing a prolactin-secreting pituitary tumor: effects of naloxone administration

In this study the effects of the implantation of the transplantable rat prolactin (PRL)-secreting pituitary tumor 7315a on gonadotropin secretion were investigated. Hyperprolactinemia was accompanied by suppressed plasma levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The total PRL content of the host's pituitary gland was decreased, but the glands of tumor-bearing animals contained greatly increased amounts of LH and FSH. Chronic administration of naloxone to tumor-bearing rats for 5 days further diminished the already suppressed total PRL content of the pituitary gland, normalized the total LH content, and did not affect the FSH content. The pituitary glands from tumor-bearing rats given naloxone showed a higher ability to release LH in vitro. Hyperprolactinemia in rats is accompanied by an increased total gonadotropin content of the pituitary gland with lowered circulating gonadotropin levels. Some of the PRL-induced changes on LH synthesis and release are mediated by opioid receptors in the hypothalamus, as naloxone administration reversed some of these effects.

Altered dopaminergic regulation of thyrotrophin release in patients with prolactinomas: comparison with other tests of hypothalamic-pituitary function

This study was carried out to test the hypothesis that sustained hyperprolactinaemia in patients with prolactinomas stimulates hypothalamic dopaminergic activity via a short loop positive feedback effect of prolactin (PRL). The intensity of dopamine (DA) effects on the pituitary around the adenoma was evaluated by measuring thyroid stimulating hormone (TSH) responses to intravenous injection of domperidone (10 mg) a new DA receptor blocking drug that does not penetrate the blood-brain barrier. TSH responses have been compared with those of PRL to the same agent. Eight females with prolactinomas showed greater TSH release after domperidone than nine normal females (sum of TSH increments over 20 min 17.5 +/- 1.7 v. 8.9 +/- 1.5 mu/l, P less than 0.001) whilst PRL release was reduced (sum of PRL increments over 120 min 5.9 +/- 2.4 v. 21.8 +/- 3.8 mu/l x 10(-3), P less than 0.01). Amongst nineteen hyperprolactinaemic females with apparently normal pituitary fossae (plain skull X-ray), ten showed an exaggerated TSH response (delta TSH, 4.2 +/- 0.6 mu/l, range 2.5-9.0 mu/1) and reduced PRL response to domperidone, comparable with established tumor cases. In the remaining nine normal fossa hyperprolactinaemic females, the TSH and PRL responses to dopaminergic were similar to normal females. These results support the initial hypothesis and indicate the coexistence of a defect in the dopaminergic inhibition of PRL release and increased dopaminergic inhibition of TSH release in patients with prolactinomas. The presence of an exaggerated TSH response to DA antagonism in a euthyroid, radiologically normal (plain skull X-ray), hyperprolactinaemic patient is compatible with the presence of an autonomously-functioning, PRL secreting, pituitary microadenoma and the TSH changes seen in these patients after DA antagonist administration can be readily detected by sensitive TSH radioimmunoassay.

The value of the thyrotropin-releasing hormone test in patients with prolactin-secreting pituitary tumors and suprasellar non-pituitary tumors

The prolactin (PRL) response to thyrotropin-releasing hormone (TRH) (delta PRL) was normal in 7 (18%) of 38 patients with clinical evidence of a prolactinoma. A negative percentage correlation between basal PRL and delta PRL was found (P less than 0.05), but a percentage correlation between tumor size and delta PRL was absent. In a survey of literature concerning 548 patients, delta PRL after TRH administration amounted to 100% or more of the basal value in 11% of patients with clinical evidence of a prolactinoma and in 9% with an adenoma proven by surgery. Hyperprolactinemia was also present in 12 of our 21 patients (57%) with suprasellar tumors not related to pituitary tumors. In 7 of 11 of these hyperprolactinemic patients (64%), the PRL response to TRH was decreased. In conclusion, the TRH test may be helpful but is not decisive in the diagnostic work-up of hyperprolactinemia patients.