Prolactin

SEX HORMONE STATUS IN MALE RATS AFTER EXPOSURE TO 50 HZ, 5 MTESLA MAGNETIC FIELD

The question of whether extremely low frequency magnetic fields can affect biological system has attracted attention. The theoretical possibility of such an interaction is often questioned and the site of interaction is unknown. The influence of extremely low frequency magnetic field of 50 Hz, 5 mTesla on sex hormone status was studied. 60 male albino rats were divided into 6 groups and were continuously exposed to 50 Hz, 5 mTesla magnetic field generated by magnetic field chamber for periods of 1, 2 and 4 weeks. For each experimental point, sham treated group was used as a control. Assay of serum testosterone LH, FSH, and prolactin were performed. Serum testosterone showed no significant changes. FSH showed significant increase than sham exposed group after 1 week magnetic field exposure. LH showed significant increase than sham exposed group only after 4 weeks magnetic field exposure, while serum prolactin hormone level showed a significant increase in all magnetic field exposed groups than sham exposed animals. Exposure to 50 Hz, 5 mTesla magnetic field for periods of 1, 2 and 4 weeks has no effect on testosterone level, some changes on FSH and LH serum levels and increase in serum prolactin level.

Frequent misdiagnosis and mismanagement of hyperprolactinemic patients before the introduction of macroprolactin screening: application of a new strict laboratory definition of macroprolactinemia

BACKGROUND

Macroprolactin (big big prolactin) has reduced bioactivity and is measured by immunoassays for prolactin when it accumulates in the plasma of some individuals. We applied normative data for serum prolactin after treatment of sera to remove macroprolactin to elucidate the contribution of macroprolactin to misleading diagnoses, inappropriate investigations, and unnecessary treatment.

METHODS

We reviewed records of women attending a tertiary referral center who had prolactin >1000 mIU/L. Application of a reference interval to polyethylene glycol (PEG)-treated hyperprolactinemic sera identified 21 patients in whom hyperprolactinemia was accounted for entirely by the presence of macroprolactin. Presenting clinical features, diagnoses, and treatment were compared in these patients and 42 age-matched true hyperprolactinemic patients.

RESULTS

Prolactin concentrations in sera of 110 healthy individuals ranged from 78 to 564 mIU/L. The range of values for the sera after PEG treatment was 70-403 mIU/L. For macroprolactinemic samples, PEG treatment decreased mean (SD) prolactin from 1524 (202) mIU/L to 202 (27) mIU/L but decreased it only from 2096 (233) mIU/L to 1705 (190) mIU/L in true hyperprolactinemic patients (P <0.01 between groups). Oligomenorrhea or amenorrhea and galactorrhea were the most common clinical features in both groups, although they occurred more frequently in true hyperprolactinemic patients (P <0.05). Serum estradiol and luteinizing hormone concentrations were significantly higher in participants with macroprolactinemia than in those with true hyperprolactinemia (P <0.05). Among participants with retrospectively identified macroprolactinemia, pituitary imaging was performed in 93% and treatment with dopamine agonist was prescribed in 87%.

CONCLUSIONS

Macroprolactin is a significant cause of misdiagnosis, unnecessary investigation, and inappropriate treatment. The use of an appropriate reference interval for the PEG immunoprecipitation procedure may be of particular importance in those patients who have an excess of both macroprolactin and monomeric prolactin.

Dysregulation of the hypothalamic-pituitary-thyroid axis in alcoholism

Thyroid dysfunction is a prominent finding in alcoholism. Subclinical and clinical hypothyroidism have been associated with clinical depression and cognitive impairment and may increase the relapse risk among alcoholics. In spite of these important clinical associations, there is no consensus on thyroid dysfunction in alcoholism in the literature. In this paper, we present a review of the literature and develop a hypothesis that may explain dysfunction of the hypothalamic-pituitary-thyroid axis in alcoholism. Based on a Medline research of the years 1980-2001 we found 33 empirical studies that assessed thyroid function in alcoholism. The most consistent findings were a reduction in total thyroxine and total and free triiodothyronine concentrations during early abstinence. About one-third of all alcoholics also displayed a blunted thyroid stimulation hormone (TSH) response in the thyrotrophin-releasing hormone test (TRH-test). Blunting was observed frequently during detoxification, but was also present in some alcoholics after several weeks of abstinence. We suggest that a reduction in peripheral thyroid hormones may be caused by a direct toxic effect of alcohol on the thyroid gland, which induces a central compensatory activation of the hypothalamic-pituitary axis with an increased TRH release. The TRH release induces a downregulation of pituitary TRH receptors, which manifest as a blunted TSH response to the TRH test. We discuss further additional effects of alcohol on thyroid-hormone metabolizing deiodinases and on monoaminergic systems, which may interact directly with mood states among abstinent alcoholics.

Plasma and pituitary thyroid-stimulating hormone levels in bromocriptine-treated New Zealand genetically hypertensive and normotensive rats

1. The effects of a 13-day intraperitoneal (i.p.) infusion of bromocriptine, delivered by osmotic pump, on plasma and pituitary thyroid-stimulating hormone (TSH) levels were investigated in New Zealand genetically hypertensive (GH) rats and their normotensive (NT) controls. 2. In both the GH and NT rats, bromocriptine significantly reduced plasma TSH level but did not have any significant effect on pituitary TSH content. 3. No significant difference was found in the plasma TSH level and pituitary TSH content between the vehicle-treated GH and NT rats. 4. These results suggest that there are no differences between the GH and NT rats with regard to the activity of the central dopaminergic system influencing TSH release and also that TSH does not play a role in the hypertension of the GH rats.

Effects of ECT on prolactin, LH, FSH and testosterone in males with major depressive illness

Fourteen males with major depressive illness (DSM-III) received a course of electroconvulsive therapy (ECT). Serum prolactin (PRL), luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone (T), were measured 15 minutes before and 15 minutes after each treatment. The severity of depression was assessed with the Hamilton Rating Scale for Depression (HRSD) two to three days before the first and two to three days following the last treatment. Post-ECT levels of PRL and LH were significantly higher than pre-ECT levels across every treatment. Changes in FSH and testosterone were not significant. There were no relationships between hormone levels (first versus last ECT) and severity of depression, including sexual functioning. It is argued that the relatively greater increases of LH than FSH is due to an acute antidopaminergic action of ECT which acts selectively on the secretion of the former. The blunted testosterone response to the increase of gonadotropins may be due to ECT-induced hyperprolactinemia.

Prolactinomas presenting as primary amenorrhoea and delayed or arrested puberty: response to medical therapy

Fourteen patients presented with arrested pubertal development associated with prolactin-secreting pituitary tumours; serum prolactin ranged from 4000-104,300 mU/l in the ten females and 920-68,000 in four males. Skull X-ray showed a markedly expanded pituitary fossa in eight patients. CT scan and/or air encephalography showed macroadenomas in nine, of whom seven had large suprasellar extensions to their tumours, yet only five had complained of headache and only two had visual field defects. All were treated with bromocriptine (7.5-60 mg/day) which lowered prolactin substantially in all and into the normal range in 11 (range less than 60-3090, median 105 mU/l). Puberty thereafter progressed spontaneously in 13, but in one patient, whose prolactin did not suppress completely, menarche could be induced only with clomiphene. Anterior pituitary function improved on bromocriptine. In seven patients with macroadenomas, tumour shrinkage into the pituitary fossa was complete and in two others incomplete shrinkage was followed by transsphenoidal hypophysectomy. Seven patients received pituitary irradiation, six after bromocriptine-induced shrinkage and one after transsphenoidal surgery. At follow-up 6 months to 10 years (median 5 years) after presentation, ten remain on bromocriptine with a suppressed serum prolactin, one has a normal prolactin after surgery, and three are off bromocriptine with residual hyperprolactinaemia (418-4680 mU/l). To date, four females have become pregnant and one male has fathered two children. Prolactinomas are an important, albeit rare, cause of arrested puberty and should therefore be sought. Most patients respond well to bromocriptine, with or without pituitary irradiation.

Possible role of prolactin in the induction of hypogonadism by chronic alcohol treatment in the male rat

Treatment of adult male rats with ethanol for a period of six weeks resulted in a numerical but not significant increase in plasma prolactin levels together with a reduction in plasma luteinizing hormone (LH) levels. Although basal plasma testosterone (T) levels were not affected in ethanol-treated animals, testicular weight was reduced and seminiferous tubules exhibited signs of atrophy. The responses of LH to luteinizing hormone releasing hormone (LHRH) and T to hCG were significantly impaired in ethanol-treated rats (p less than 0.01). Treatment with bromocriptine (1 mg/kg body weight/day), resulted in the expected decrease in plasma levels of prolactin and an increase in basal plasma LH levels to the levels found in control groups. Basal plasma T levels were not affected by bromocriptine. However, both plasma LH responses to LHRH and plasma T responses to hCG were significantly improved by bromocriptine treatment in alcoholic rats and became similar to the responses measured in control animals. The results suggest that bromocriptine-induced suppression of prolactin release has a beneficial effect on ethanol-induced hypogonadism.

Apomorphine-induced behaviour during the oestrous cycle of the rat

The effect of various doses of apomorphine (APO) (25, 250, 400 and 750 micrograms/kg, s.c.) on open field behaviour, stereotyped behaviour, body temperature and concentrations of serum oestradiol was studied in cycling females and in ovariectomized rats. With the exception of grooming, the hormonal variations during the cycle, or the ovariectomy, did not have an effect on behaviour related to stimulation of presynaptic dopamine (DA) receptors. The endocrine status on proestrus (PE), characterized by an increase in serum oestradiol, did influence hyperlocomotion and hypothermia induced by apomorphine; the former being attenuated and the latter increased, as compared to the other phases of the cycle. Ovariectomy resulted in an increase in the stimulatory effect of apomorphine on locomotion. Stereotypy induced by apomorphine was unaltered by hormonal variations during the cycle and it was slightly attenuated by removal of the ovaries. During phases of low levels of oestrogen (oestrus, metestrus) apomorphine significantly increased the levels of serum oestradiol, determined 30 min after the administration of drug. It is concluded that the various DAergic mechanisms in brain are differentially affected by hormonal variations during the cycle and by ovariectomy.

The influence of thyroid disorders on the dopaminergic regulation of prolactin, thyrotropin and growth hormone

In order to clarify if hyper- and hypothyroidism change by feed-back mechanisms the dopaminergic controlled release of PRL, TSH and GH, the serum values of these hormones were measured before and following iv administration of 5 mg metoclopramide in 10 hyperthyroid, 11 euthyroid and 10 primary hypothyroid age-matched females, all consecutively investigated. The secretion pattern, as well as the quantitated response (area under the curve - AUC) of PRL were identical for the three groups, and uninfluenced by thyroid status. By contrast the TSH responses (AUC) were significantly and positively correlated to the basal TSH, suggesting that the effect of metoclopramide was dependent on the secretory capacity of the thyrotropic cells. The serum GH level was found to decrease in all three groups following metoclopramide, probably due to the inhibition of release. Stimulation of the same subjects with 200 micrograms TRH iv resulted in response curves of serum PRL and TSH, which were significantly and positively correlated to the basal serum TSH. The serum values of GH increased following TRH in the hypothyroid group, while the values of the hyperthyroid were depressed and unchanged. The present results suggest that the dopaminergic tonus on PRL, TSH and GH secretion is unaffected by thyroid feed-back mechanisms. The TRH-induced release of each of the three hormones is, however, dependent on thyroid status.

Divergent effects of prolactin on 4-ene-5 alpha-reductase activity and production of C19-steroids from progesterone in immature rat ovary

Female rats of the Sprague-Dawley strain were used. Two pituitaries from 9-week old rats were grafted in both kidneys of 21-day old rat to induce hyperprolactinemia. All rats with or without pituitary isografts were hypophysectomized on day 26. Starting from day 29, the rats in groups of 8-11 were injected daily with 5 micrograms NIH-LH-S19 or saline for 3 days. Ovarian homogenates from these rats on day 32 were incubated with [14C]4-androstene-3,17-dione or [3H]progesterone and steroid metabolism was estimated. In the hypophysectomized rat ovary, the 5 alpha-reductase activity was stimulated significantly by LH. Although pituitary isograft alone had no stimulative effect on 5 alpha-reductase activity of the hypophysectomized rat ovary, concomitant treatment with LH and pituitary isograft (prolactin) had an additive effect. Formation of the sum of C19-steroids from progesterone in the hypophysectomized rat ovary was stimulated markedly by LH but reduced slightly by prolactin. The LH-induced production of C19-steroids from progesterone was inhibited markedly by prolactin. These results indicate that prolactin treatment inhibits basal and LH-induced production of C19-steroids from progesterone but stimulates LH-induced 4-ene-5 alpha-reductase activity in immature rat ovary.

Excitation by dopamine of putative oxytocinergic neurones in the rat supraoptic nucleus in vitro: evidence for two classes of continuously firing neurones

Neurones from the supraoptic nucleus in the rat hypothalamic slice preparation in vitro have been recorded from using conventional extracellular techniques. Neurones which fired in a slow continuous manner (putative oxytocinergic cells) increased their firing pattern in response to dopamine applied in the perfusate or pressure ejected onto the slice. Of these neurones, 85% were inhibited by spiperone, haloperidol or cis-flupenthixol applied in the bath. A small proportion (approximately 15%) of neurones excited by dopamine (DA) were not affected by these DA antagonists but were inhibited strongly by (+/-)-sulpiride. Similar results were also obtained on a small number of cells recorded from an 'island-slice' preparation, utilized to isolate the observed responses to an area immediately adjacent to the supraoptic nucleus. These results may be relevant to earlier work on in vivo anaesthetized preparations using intracerebroventricular injections of DA and antagonists, and indicate that such substances may act directly on a synapse(s) within the magnocellular nucleus in addition to other possible actions within the neurohypophyseal tract. The differential response to the dopamine antagonists indicate that the majority of continuously firing neurones in the supraoptic nucleus are of the DI receptor class, but the presence of possible D2 receptors on a small proportion of these neurones suggests that a second type of continuously firing neurone may exist in this nucleus.

An inverse correlation between spontaneous eye-blink rate and platelet monoamine oxidase activity

An inverse correlation between platelet monoamine oxidase activity and spontaneous eye-blink rate, a putative measure of central dopaminergic activity, was found in medication-free chronic schizophrenic patients without tardive dyskinesia (n = 20, rs = -.47, P less than .025). A similar correlation was found when patients with tardive dyskinesia were included but was weaker (n = 27, rs = -.35, P less than .05). Normal controls and patients with tardive dyskinesia did not demonstrate this relationship. This report confirms a previous finding of a significant platelet monoamine oxidase-blink rate correlation in chronic schizophrenic patients. Insofar as this relationship is mediated by dopamine, it suggests that dopaminergic relations are more readily demonstrated in schizophrenic subjects than normals. Moreover, tardive dyskinesia appears to obscure this dopaminergic relationship.

Galactorrhoea, hyperprolactinaemia, and pituitary adenoma presenting during metoclopramide therapy

A 49-year-old woman presented with a one month history of headaches, loss of libido and galactorrhoea. She had been taking metoclopramide for the previous 3 months for reflux oesophagitis. She was found to have substantially elevated serum prolactin levels and a pituitary adenoma, which have not been previously described in a patient taking metoclopramide. The drug was stopped and the serum prolactin level fell progressively to normal with resolution of symptoms over 4 months. This suggested that contrary to our original impression that she had a prolactin-secreting pituitary adenoma which had been stimulated by metoclopramide, she had metoclopramide-induced hyperprolactinaemia and an incidental pituitary tumour.

Surgical treatment of pituitary prolactinomas: postoperative prolactin and fertility in seventy patients

The surgical results obtained in 70 patients with pituitary prolactinomas indicate that the success of surgery depends on the preoperative prolactin level and the diameter of the adenoma, and that the former is the more influential factor. Assessment of both of these parameters affords a good prediction of the endocrine result. The cure rates for different patient groups ranged from 4% to 90%. Postoperative results in women (57% with normal prolactin levels) were better than those in men (17% with normal prolactin levels). Of 19 women who desired pregnancy, 11 (58%) achieved successful pregnancies; 1 woman became pregnant twice. In addition, one woman had an extrauterine pregnancy and one suffered a spontaneous abortion. Five required additional bromocriptine therapy. The data were evaluated analytically.

Pyrexia of unknown origin. Presenting sign of hypothalamic hypopituitarism

A 62-year-old man was admitted to hospital 10 times over 12 years because of pyrexia of unknown origin. Hypothalamic hypopituitarism was diagnosed by dynamic tests including clomiphene, LRH, TRH and chlorpromazine stimulation. Lack of ACTH was demonstrated by long and short tetracosactrin tests. The aetiology of the disorder was believed to be previous encephalitis. Following substitution therapy with adrenal and gonadal steroids there were no further episodes of fever.

The role of D-1 and D-2 receptors

Dopamine receptors in intracerebral motor and endocrine systems have been divided into two main types, D-1 and D-2, dependent on the presence or absence of adenylate cyclase linkage. Here we have investigated a number of dopamine agonist and antagonist drugs in man that have different actions on D-1 and D-2 receptors in animals. Motor and endocrine effects in parkinsonian subjects seem to depend on drug interaction with D-2, but not D-1, receptors. These results may have important implications for the design of anti-parkinsonian and antipsychotic agents.

Pituitary function tests in Sheehan's syndome

Fourteen patients with a typical history of Sheehan's syndrome underwent pituitary function tests with simultaneous injections of 100 micrograms LH-RH, 200 micrograms TRH and 0.05--0.1 units of soluble insulin per kg body weight. Serum prolactin levels remained unchanged in all of eleven subjects given TRH. GH levels did not rise after hypoglycaemia in five subjects. In contrast serum LH and FSH rose significantly in twelve out of fourteen subjects given LHRH and serum TSH rose significantly in five out of seven subjects given TRH. It is concluded that pituitary function is relatively preserved for LH and FSH but not for prolactin and GH in Sheehan's syndrome. It is further suggested that absence of a rise in prolactin following TRH stimulation may provide the most sensitive test of pituitary hypofunction in postpartum haemorrhage.

Successful outcome of ergocryptine-induced pregnancies in twenty-one women with prolactin-secreting pituitary adenomas

The natural history of prolactin-secreting adenomas is not known. For this reason, optimal therapy for women harboring these adenomas who desire to conceive is also unknown. Argument can be found to favor surgical excision, radiation therapy, prolactin-suppressing chemotherapy, and clinical observation. In a large series of women with prolactin-secreting pituitary adenomas, 21 have conceived and delivered healthy infants, all of whom had ergocryptine-induced prolactin suppression as the sole form of therapy. Endocrinologic, neurologic, biochemical, and radiologic assessment failed to demonstrate any obvious growth of the pituitary adenoma, except for slight enlargement of the sella turcica in one patient who delivered twins. The failure to demonstrate any worsening of the clinical state may reflect the fact that no large tumors were included in this series, only small but definite microadenomas found on sellar tomography. All of the various modalities of therapy must be considered with each patient, but this series suggests that ergocryptine treatment with careful clinical follow-up is relatively safe in patients with small pituitary tumors.

Maternal serum prolactin and its response to TRH in normal and complicated early pregnancy

Maternal serum prolactin levels (PRL) were measured by radioimmunoassay in thirty-four women with either normal or complicated early pregnancy. The basal PRL level (mean +/- S.D.) of 33.4 +/- 16.4 ng/ml in normal pregnancy (n = 15) was similar to the level of 32.7 +/- 18.8 ng/ml in threatened abortion (n = 11) and 32.8 +/- 16.9 ng/ml in hyperemesis gravidarum (n = 8). Two patients, one with blighted ovum and the other with subsequent spontaneous abortion, demonstrated PRL levels lower than the range of 20-63 ng/ml in the control group. The PRL response to 200 microgram of synthetic thyrotropin releasing hormone (TRH) administered intravenously was similar throughout the patient groups. The basal level of PRL in the whole series was more closely related to the level of serum oestradiol (r = 0.778, P less than 0.001) than to that of serum progesterone (r = 0.442, P less than 0.05). However the increments of PRL following TRH administration did not correlate with either oestradiol or progesterone.

Hyperprolactinaemia and hypogonadism in men: response to exogenous gonadotrophins

Three male patients with pituitary tumours and marked hyperprolactinaemia were investigated. Their prolactin (PRL) levels ranged from 210 to 2500 ng/ml. The subjects had clinical and laboratory characteristics of hypogonadotrophic hypogonadism. All were treated with human chorionic gonadotrophin (HCG) and in one subject human menopausal gonadotrophin (HMG) was given in addition. In all three patients, despite the persistence of hyperprolactinaemia, serum testosterone had risen to normal levels within 4--17 days after starting HCG. Despite the normal testosterone level, impotence persisted in two patients and the third had persistently decreased libido. The hypogonadism in these patients may be related to an absolute reduction in gonadotroph number secondary to destruction by tumour mass. Alternatively, hyperprolactinaemia may inhibit the synthesis or release of the gonadotrophins or LHRH. Despite hyperprolactinaemia, pharmacological doses of HCG induced testosterone secretion in all these three subjects.

Hypothyroidism in pregnancy

Two mothers with hypothyroidism gave birth to normal infants. In one patient there was good evidence that maternal hypothyroidism improved during the last trimester due to placental transfer of fetal thyroid hormone. If pregnancy is advanced when the diagnosis of hypothyroidism is made, it would seem that replacement therapy may be withheld without detriment to the fetus.

The borderline pituitary fossa in patients with amenorrhoea and/or galactorrhoea

A retrospective clinicoradiological study of 80 patients with amenorrhoea and/or galactorrhoea showed: 1. Of 60 patients, in whom prolactin levels were estimated, 28 (47%) had hyperprolactinaemia (serum prolactin levels greater than 20 ng/ml). 2. Hyperprolactinaemia was present in 85% of patients with amenorrhoea and galactorrhoea, 35% of those with galactorrhoea only, and 12.5% of those with only amenorrhoea. 3. Pituitary adenomas were surgically removed from six patients; all but one had prolactin levels over 100 ng/ml. The level was 53 ng/ml in the sixth patient. 4. There is a considerable degree of observer variation in the interpretation of borderline sellar changes. 5. Minor abnormalities of the pituitary fossa were noted in 64% of patients with hyperprolactinaemia and 36% of those with normal prolactin levels. 6. The highest incidence of perfectly normal sellae was among patients with either amenorrhoea or galactorrhoea and normal serum prolactin.