Impaired prolactin stimulation by estrogens in man (original) (raw)
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International Journal of Molecular Sciences
Estrogen signaling plays an important role in pituitary development and function. In sensitive rat or mice strains of both sexes, estrogen treatments promote lactotropic cell proliferation and induce the formation of pituitary adenomas (dominantly prolactin or growth-hormone-secreting ones). In male patients receiving estrogen, treatment does not necessarily result in pituitary hyperplasia, hyperprolactinemia or adenoma development. In this review, we comprehensively analyze the mechanisms of estrogen action upon their application in male animal models comparing it with available data in human subjects. Sex-specific molecular targets of estrogen action in lactotropic (PRL) cells are highlighted in the context of their proliferative and secretory activity. In addition, putative effects of estradiol on the cellular/tumor microenvironment and the contribution of postnatal pituitary progenitor/stem cells and transdifferentiation processes to prolactinoma development have been analyzed. ...
Acta medica portuguesa, 1980
Basal levels of prolactin (PRL) and estradiol (E 2 ) were studied in 10 adolescents with gynecomastia who were at stages II to IV of their sexual development. In 7 of the 10 patients, the hypophyseal response of PRL to the administration of sulpiride was assessed: 5 of the 7 received 25 mg i.m., and the remaining 50 mg. i.m. The 10 cases were compared with 12 control boys without gynecomastia matched for stage of sexual development. Five of the controls were given 25 mg of sulpiride i.m. and the other 50 mg. Basal PRL levels were the same in both groups. Sulpiride stimulates the secretion of PRL in boys with and without gynecomastia. However, a significantly increased circulating E 2 level was found in patients with gynecomastia.
Prolactin Pulsatility in Patients with Gonadal Dysfunction
Clinical Endocrinology, 1981
Serum prolactin concentrations have been measured at 15 min intervals for 2 h on 240 occasions in 227 patients with symptoms which could have been due to hyperprolactinaemic gonadal dysfunction. Of the 227, 138 had at least one elevated random prolactin level. Overall, 22% showed no significant fluctuation in prolactin. In 38% the levels fell progressively from the start of the sampling period, this pattern being found most commonly in patients complaining of infertility. The sampling method yielded a basal or unstressed prolactin concentration which was, on average, 27% lower than random prolactin concentrations. However, a comparison with clinical data, the radiological appearances of the pituitary fossa, and the response to bromocriptine therapy, has shown that there is no predictive information in the multiple sampling results that could not have been obtained from two or three random prolactin levels.
Prolactin and testosterone: their role in male sexual function
International Journal of Andrology, 1996
The role of androgens in the sexuality of men is still not completely clear. Men with severe hyperprolactinaemia frequently show mild hypogonadism, and many complain of loss of libido and penile erectile dysfunction (ED). We studied the nightsleep related erections and the penile response to visual erotic stimuli (VES) in 44 men: 13 with severe hypogonadism (Group 1; serum testosterone <1.4 ng/ml), 10 with mild hypogonadism (Group 2; serum testosterone 2-3.5 ng/ml), nine with severe hyperprolactinaemia and mild hypogonahsm (Group 3) and 12 control men (Group 4). AU of the patients complained of loss of libido and ED. Group 1 showed significantly impaired night erections when compared with any of the other three groups, but no differences were detected between Groups 2, 3 and 4. The penile response to VES did not show any significant difference between the four groups, but was lower in Group 1 than in Group 4. These data confirm that night erections are androgen-dependent, but also suggest that there are two thresholds for serum testosterone: one below which sexual behaviour is impaired with normal night erections, and a lower threshold below which night erections are also impaired. The penile response to VES was confirmed as being only partially androgen-independent. Furthermore, hyperprolactinaemia does not affect night erections or the penile response to VES, suggesting that its effect on libido and sexual behaviour is due mainly to modulation of the psychological pattern of the patient.
Proceedings of the National Academy of Sciences, 1979
Male rats received acute or chronic primary or acute secondary stimulation with estradiol, and the effects on pituitary prolactin synthesis and its mRNA accumulation were examined. Prolactin synthesis was determined by the in vitro incorporation of [ 3 H]leucine into prolactin over a period of 1 hr. Prolactin mRNA was measured both by cell-free translation in a nuclease-treated rabbit reticulocyte lysate and by hybridization to the complementary DNA. The latter two methods gave similar results under all experimental conditions. Acute primary stimulation with estradiol produced a significant increase in pituitary prolactin mRNA accumulation at 12 hr, which further increased by 2- to 3-fold over the next 48 hr. In contrast, no increase in prolactin synthesis was observed during the first 24 hr. Chronic stimulation with estradiol induced increases of both prolactin synthesis and prolactin mRNA that were quantitatively indistinguishable over the period of 1-4 weeks, reaching a plateau a...
Estrogen in the adult male reproductive tract: a review
Reproductive biology and endocrinology : RB&E, 2003
Testosterone and estrogen are no longer considered male only and female only hormones. Both hormones are important in both sexes. It was known as early as the 1930's that developmental exposure to a high dose of estrogen causes malformation of the male reproductive tract, but the early formative years of reproductive biology as a discipline did not recognize the importance of estrogen in regulating the normal function of the adult male reproductive tract. In the adult testis, estrogen is synthesized by Leydig cells and the germ cells, producing a relatively high concentration in rete testis fluid. Estrogen receptors are present in the testis, efferent ductules and epididymis of most species. However, estrogen receptor-alpha is reported absent in the testis of a few species, including man. Estrogen receptors are abundant in the efferent ductule epithelium, where their primary function is to regulate the expression of proteins involved in fluid reabsorption. Disruption of the alph...
Neuroendocrinology Letters, 1984
The prolactin (PRL) response to thyrotropin-releasing hormone (TRH) was evaluated in 686 patients over a 4-year period. Of the 170 control subjects tested, none had a blunted PRL response to TRH. Eighty patients with prolactinomas documented by surgery were tested. Ninety-five percent (76 of 80) of these patients had an abnormally blunted PRL response to TRH. Of the 87 patients with a prolactinoma who did not undergo surgery, 98% (85 of 87) had a blunted PRL response to TRH. Many patients with other pituitary and hypothalamic diseases (pituitary tumors other than prolactinomas [Cushing's disease, acromegaly, chromophobe adenoma], craniopharyngioma) also had an abnormal PRL response to TRH (79 of 153, 52%). In the majority of patients with hyperprolactinemia due to dopamine antagonist medications, TRH stimulation did not produce a normal rise in PRL. The TRH test may be helpful in confirming the diagnosis of prolactinoma, but it is not a decisive factor in the diagnosis or management of this entity. Fertil Steril43:66, 1985; Hyperprolactinemia is a common finding in women with oligomenorrhea or amenorrhea. 1 The processes which most commonly cause hyperprolactinemia include: pituitary or hypothalamic disease, drugs which are dopamine antagonists, hypothyroidism, pregnancy, and chronic renal failure. 2 To aid in the differential diagnosis of
Human Prolactin: Measurement in Plasma by In Vitro Bioassay
Journal of Clinical Investigation, 1971
tracted human plasma by a sensitive and specific in vitro bioassay. Secretory activity of breast tissue fragments from mid-pregnant mice, incubated in organ culture with human plasma, serves as the histologic end point. Sensitivity is 5 ng/ml (0.14 mU/ml) or somewhat better for ovine prolactin, and approximately 0.42 mU/ml for prolactin activity of human plasma at the dilutions used in the assay. Human growth hormone as it circulates in blood, like the material extracted from pituitary glands, is strongly lactogenic. Antisera to human growth hormone are capable of completely neutralizing the prolactin effect of large amounts (600 ng/ml) of human growth hormone added to the system. Plasma prolactin activity is less than 0.42 mU/ml in normal men and women. Of 26 patients with nonpuerperal galactorrhea, 14 had elevated prolactin activities ranging from 0.42 to 3.5 mU/ml. Growth hormone levels by radioimmunoassay were far too low, in general, to account for the observed prolactin activity. All of 14 nursing mothers, 1-30 days post partum, had elevated prolactin activity with a mean of 2.29 and a total range of 0.56-4.5 mU/mi. Growth hormone was in the low normal range in all of these subjects. Seven patients on psychoactive drugs of the phenothiazine series similarly had elevated prolactin activity with low growth hormone. Antiserum to human growth hormone, when preincubated with plasma samples from each of these three groups of subjects, produced no significant inhibition of prolactin activity. In two acromegalic patients with markedly elevated growth hormone levels, antiserum to growth hormone produced complete inhibition of prolactin activity in one and partial inhibition in the other. These studies indicate that human growth hormone and human prolactin This work was presented in part at the Annual Meeting of the American Federation for Clinical Research, Atlantic City, N. J., May 1970 (1).
Reproductive Biology and Endocrinology Estrogen in the adult male reproductive tract: A review
Testosterone and estrogen are no longer considered male only and female only hormones. Both hormones are important in both sexes. It was known as early as the 1930's that developmental exposure to a high dose of estrogen causes malformation of the male reproductive tract, but the early formative years of reproductive biology as a discipline did not recognize the importance of estrogen in regulating the normal function of the adult male reproductive tract. In the adult testis, estrogen is synthesized by Leydig cells and the germ cells, producing a relatively high concentration in rete testis fluid. Estrogen receptors are present in the testis, efferent ductules and epididymis of most species. However, estrogen receptor-α is reported absent in the testis of a few species, including man. Estrogen receptors are abundant in the efferent ductule epithelium, where their primary function is to regulate the expression of proteins involved in fluid reabsorption. Disruption of the α-receptor, either in the knockout (αERKO) or by treatment with a pure antiestrogen, results in dilution of cauda epididymal sperm, disruption of sperm morphology, inhibition of sodium transport and subsequent water reabsorption, increased secretion of Cl -, and eventual decreased fertility. In addition to this primary regulation of luminal fluid and ion transport, estrogen is also responsible for maintaining a differentiated epithelial morphology. Thus, we conclude that estrogen or its α-receptor is an absolute necessity for fertility in the male.