Human Pituitary Prolactin Research Articles

Lactogenic Hormones, Fetal Nutrition, and Lactation

In 1962 when John B. Josimovich, MD, was a postdoctoral fellow, he published a fundamental paper on human placental lactogen. Interest in the function and characterization of the peptide grew rapidly. More recently, it was established that human pituitary prolactin (P) exists apart from pituitary growth hormone (GH), and elucidation of its role is progressing. According to our current understanding, the placentally produced placental lactogen, now termed chorionic somatomammotropin (CS), directs maternal metabolism to ensure fetal nutrition. Postpartum P production is required for lactation, and thereby plays an integral role in nutrition of the neonate. Because nutrition of the fetus and neonate commands the attention of both pediatric investigators and practicing pediatricians, the volume Lactogenic Hormones, Fetal Nutrition, and Lactation deserves the attention of both groups. The book successfully presents recent discoveries in the basic biology of CS and P and their clinical applications. The chapters are by eminent basic

Short-term variation in blood levels of prolactin, luteinizing hormone and follicle-stimulating hormone in normal men throughout the day.

The release of prolactin may be related to that of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (Bern & Nicoll, 1968). The present study was designed to determine whether there is any relationship between the short-term variation in blood LH and FSH levels (Naftolin, Yen & Tsai, 1972; Nankin & Troen, 1972), and that of prolactin levels in the blood. A total of 230 blood samples were obtained from five normal men (age 24–29) at 15-min intervals between 09.00 and 16.30 h. All subjects continued their normal daily routine during the experiment. Samples were collected through an indwelling Polythene cannula, and the plasma was separated and stored at −20 °C. Prolactin levels were determined by radioimmunoassay (McNeilly, 1973). The results are expressed as ng standard human pituitary prolactin (kindly provided by Dr H. Friesen)/ml. Serum LH and FSH were measured by double-antibody radioimmunoassay as described by McNeilly & Chard (1974).

Factors influencing the secretion of human prolactin and growth hormone in menstrual and gestational women

Human pituitary prolactin (PRL) is released in a pattern that is different from growth hormone (HGH). Basal PRL concentrations remain unchanged throughout the menstrual cycle and bear no apparent relationship to the cyclic change in gonadotropins. Significant increases in PRL occur after intramuscular chlorpromazine (CPZ). The response is dose related. These results correlate with PRL values measured in patients ingesting large amounts of phenothiazines for psychiatric disease. Thyrotropin-releasing hormone (TRH) provokes the release of PRL as well as thyroid-stimulating hormone (TSH). TRH-induced PRL release during menses is similar to that found at midcycle. On the other hand, HGH secretion remains unaffected by CPZ and TRH. Throughout pregnancy, basal plasma PRL rises to a mean of 214 ng. per milliliter at term. In spite of this, PRL levels rise even higher in response to intravenous TRH. Postpartum, puerperal PRL levels increase in response to nursing and intravenous TRH but not after intranasal oxytocin. The post-TRH response can be dissociated from the PRL response to nursing especially beyond 60 postpartum days. Elevations in endogenous PRL secretion are followed by changes in breast function within three hours. These changes include engorgement with increased milk production and letdown. No such changes occur after intravenous TRH in pregnancy. Intravenous TRH appears to be a specific stimulus to PRL release and is without significant side effects. These studies suggest that PRL may promote breast milk production in lactating women. The mammary response to elevated PRL concentrations may be modified, however, by the concentration of endogenous estrogen and progesterone since no breast engorgement followed the post TRH-PRL rise before delivery. There is no similarity between the secretion of PRL and HGH in pregnancy.

Thyrotropin releasing factor (TRF) effect on secretion of human pituitary prolactin and thyrotropin in children and in idiopathic hypopituitary dwarfism: further evidence for hypophysiotropic hormone deficiencies.

ABSTRACT Synthetic thyrotropin-releasing factor (TRF) administered iv induced a significant rise within 5 min in the concentration of plasma prolactin and plasma TSH in 13 children with constitutional short stature (Group I), 13 patients with isolated growth hormone deficiency (Group II), and in 13 patients with idiopathic hypopituitary dwarfism, including TSH deficiency (Group III). The mean peak concentration of plasma prolactin was 25.2 ng/ml for Group I, 27.7 ng/ml for Group II, and 20.9 ng/ml for Group III. These values were not significantly different from one group to another. The mean peak concentration of plasma TSH was 20.7 μU/ml for Group I, 19.1 μU/ml for Group II, and 26.0 μU/ml for Group III. One patient with multiple pituitary hormone deficiencies had no detectable TSH rise (<1.5 μU/ml) following TRF, but had a normal rise in plasma prolactin of 20 ng/ml. The TRF stimulation test provides a means to distinguish primary from secondary hypopituitarism. These data provide further evidence that...

HUMAN PITUITARY PROLACTIN DURING PREGNANCY AND POST PARTUM AS MEASURED IN SERUM BY A RADIOIMMUNOASSAY

Human pituitary prolactin (HPr) was measured using its cross reaction with sheep prolactin in a radioimmunoassay initially developed by Davis et al. (1971). The proposed system has been proved to be suitable for specific measurement of HPr contained in 200 μl of human serum (Midgley and L’Hermite; to be published). There was no inhibition of the binding of the tracer (highly purified ovine prolactin; LER-860-2) to the anti-ovine prolactin serum by as much as 2500 IU of human chorionic gonadotrophin (Commercial HCG, Roussel), 500 ng of human growth hormone (HGH-HS1394) and 10 μg of human chorionic somatomammotropin (HCS, Lederle 717.340). Immunoreactive HPr was measured in serum with reference to a pool of serum collected from pregnant women. This pool was temporarily used as laboratory standard. An immunological activity of 1.0 Unit (U) has been arbitrarily attributed to the amount of HPr contained in 1.0 ml of this pool.

PROLACTIN RELEASE AFTER INJECTION OF THYROTROPHIN-RELEASING HORMONE IN MAN

Five normal men were injected intra Summary venously 200 μg. of synthetic thyrotrophin-releasing hormone (T.R.H.). Blood was collected every 5 or 10 minutes and assayed for thyroid-stimulating hormone (T.S.H.), human growth hormone, luteinising hormone, hydrocortisone, and pituitary prolactin. T.S.H. levels reached peak values 20 to 40 minutes after the injection. Hydrocortisone, H.G.H., and L.H. did not exhibit any systematic variation. The T.R.H. injection was followed within 5 minutes by a release of prolactin, with a peak value at 10 minutes. These data indicate a lack of specificity of T.R.H. and suggest that in man it acts as a prolactin-releasing factor. Intravenous T.R.H. administration should become a very useful clinical test for the investigation of the hypothalamo-pituitary relationships, with special respect to prolactin secretion.

Human placental lactogen and human pituitary prolactin.

Human placental lactogen and human pituitary prolactin.

Radioimmunoassay of a human pituitary prolactin in plasma.

A protein fraction with prolactin bioactivities was obtained from the culture medium of human fetal pituitary tissue in long term cultures and termed Pasteels human prolactin (PHP) for convenience. An antiserum was prepared against this human prolactin and used to develop a radioimmunoassay for the material in human plasma. The antigen available (220 µg)was tested against antisera to human growth hormone and to human placental lactogen and in radioimmunoassays for these hormones. The results suggested that the human prolactin fraction contained some immunoreactive human growth hormone (1%). The resulting antibodies in the antihuman prolactin serum could be neutralized by the addition of human growth hormone. The human prolactin also generated antibodies, binding &lt;sup&gt;131&lt;/sup&gt;I-labelled human prolactin, which were not neutralized by human growth hormone. This binding was inhibited by plasma from a normal male, 2 normal females and by plasma from a lactating woman after breast feeding. An increase in plasma concentration of the inhibitor, immunologically similar to the human prolactin fraction, was obtained after phenothiazine injection. In the 7 plasma samples tested for human prolactin only 1 contained a detectable concentration of immunoreactive growth hormone. Immunoreactive human placental lactogen (human chorionic somatomammotropin) or any material cross-reacting with anti-HCS serum was undetectable in these plasma samples by a sensitive radioimmunoassay. It is suggested that human plasmas contain detectable amounts of a material immunologically similar to a prolactin fraction isolated from tissue cultures of fetal pituitaries. The fraction and the plasma inhibitor are distinguishable by immunoassay from human growth hormone and from human placental lactogen.

A study of prolactin-like activity in individual human pituitary glands.

SUMMARY Polyacrylamide disc gel electrophoresis of aqueous extracts of individual human anterior pituitary glands failed to identify a protein with lactogenic activity which was characteristic of pregnancy and the post-partum period. Lactogenic activity, determined by a semi-quantitative rabbit mammary gland organ culture assay, was largely associated with the growth hormone fraction. The total prolactin activity of individual anterior pituitary glands was determined by a 'local' intradermal pigeon crop sac method. The glands from pregnant and parturient women did not contain a higher concentration of prolactin than those of men or non-pregnant non-lactating women. These results do not provide any evidence for the existence of a human pituitary prolactin distinct from growth hormone. Reasons for this are discussed.