Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PROLACTIN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources
PubMedDate not supplied

[Diurnal rhythm and the effect of hemodialysis therapy on blood prolactin levels in patients with chronic renal insufficiency].

In 97 patients with different stages of chronic renal failure prolactin serum level was determined, and its diurnal rhythm and dependence on haemodialysis treatment were studied. Diurnal rhythm was investigated in 6 men and 6 women with advanced chronic renal failure on diet and other symptomatic treatment. A normal diurnal rhythm of prolactin was recorded only in 3 patients, two of them being with elevated basal prolactin levels; an abnormal prolactin rhythm was documented in 8 patients. In 4 patients no evident diurnal changes in prolactin level were observed, though 3 of them had a normal basal prolactin level. In one patient slight fluctuations of the prolactin level were recorded, while in 4 other patients an abnormal type of diurnal rhythm was observed. Prolactin determinations in patients on maintenance haemodialysis showed increased values in 45 men (719 + 122 mIU/l) as well as 34 women (1251 + 171 mIU/l). The analysis of the influence of haemodialysis on cuprophane and polyacrylonitrile membrane was made in 6 patients and no difference was shown between predialysis and postdialysis serum prolactin values, as well as in values obtained for non-dialysis and dialysis days. The results obtained in this study showed an absent or abnormal diurnal rhythm of prolactin in 75% of patients with chronic renal failure. In patients on maintenance haemodialysis increased prolactin levels were found. Haemodialysis procedure on cuprophane and polyacrylonitrile membrane failed to affect the serum level of prolactin.

Adult↗
PubMed1998

The study of a physiological significance of prolactin in the regulation of calcium metabolism during pregnancy and lactation in rats.

Since a pharmacological dose of prolactin has previously been reported to enhance calcium absorption and bone calcium turnover, the role of endogenous prolactin in the regulation of calcium metabolism was investigated in the balance studies of Wistar rats between days 17 and 20 of first (P1) and fourth (P4) pregnancy and between days 12 and 15 of lactation (L). Each group was divided into 3 subgroups: one subgroup was given 0.9% NaCl (control); one was given 0.3 mg bromocriptine/100 g body weight ip twice daily for 3 days (to suppress prolactin secretion); and one was given bromocriptine and 0.25 mg prolactin/100 g body weight sc daily for 3 days. All three groups received 1 mL/100 g body weight of 1.25 mM calcium gluconate containing 2 mCi (1 Ci = 37 GBq) 45Ca daily for 3 days. Compared with the two pregnant controls, the L group had higher food consumption and higher fecal calcium excretion and lower urinary calcium excretion (% intake). Bromocriptine administration increased total calcium excretion from 59% intake to 84 and 66% intake in P1 and P4, respectively, suggesting that endogenous prolactin decreased total calcium excretion. On the other hand, exogenous prolactin had no effect on the calcium balance of P1 but increased the total calcium excretion in P4 from 57 to 66% intake. In contrast, the calcium balance of lactating rats was not altered by suppression of endogenous prolactin secretion or exogenous prolactin. Considering bone 45Ca content as representing bone Ca turnover, a lower value of bone 45Ca content indicated an accelerated bone Ca turnover. It was found that bromocriptine had no effect in P1 but decreased bone Ca turnover rate in the P4 and L groups, indicating an accelerating effect of endogenous prolactin on bone Ca turnover in the P4 and L groups. Exogenous prolactin, on the other hand, decreased bone Ca turnover rate in every group. Muscle Ca turnover was affected by bromocriptine and exogenous prolactin in the same manner as bone 45Ca contents. Interestingly, the biphasic action of prolactin was demonstrated in both calcium absorption and bone calcium turnover. It could be concluded that during pregnancy and lactation, endogenous prolactin increases food consumption, fractional calcium absorption, and bone calcium turnover, apparently to increase calcium availability for fetal development and milk calcium secretion.

Analysis of Variance↗
PubMed2002

Expression of functional prolactin and its receptor in human colorectal cancer.

BACKGROUND AND AIMS: Ectopic production of prolactin has been reported for several tumors, and elevated prolactin plasma levels have been detected in colorectal cancer patients. However, the role of prolactin in colorectal cancer remains unclear. We therefore compared expression patterns of prolactin and its receptor in normal and neoplastic colonic mucosa of the same patient with noncancer controls and determined mitogenic effects in vitro. MATERIALS AND METHODS: mRNA and protein expression was analyzed by semiquantitative RT-PCR and western blotting. Localization of ligand and receptor in tissues was investigated by immunohistochemistry. Mitogenic effects of prolactin on colorectal cancer cell lines (Caco-2, HT-29, LoVo) were assayed by [(3)H]thymidine incorporation. RESULTS: mRNA expression of prolactin was detected in 13% of normal and 27% of cancer specimens, with the highest levels seen in moderately differentiated tumors. Receptor mRNA was amplified from the majority of normal (96%) and cancer (94%) samples with an overexpression seen in tumor tissues. Protein expression of prolactin was detected in cancer tissues only, with the highest levels seen in moderately differentiated tumors. Receptor protein expression was correlated with the RT-PCR data, showing up to fourfold overexpression in tumor tissues. Staining for both ligand and receptor was observed in epithelial cells. DNA synthesis was significantly stimulated by prolactin in all cell lines reaching 167-197% of unstimulated controls. CONCLUSION: Expression of prolactin, overexpression of prolactin receptors in colorectal cancers, and mitogenic effects of prolactin suggest a role for this hormone in a subgroup of colorectal cancers, which is presumably mediated by paracrine/autocrine pathways.

Actins↗
PubMed1980

Blunted prolactin response to hypoglycemia in patients with hypothalamic-pituitary disease and in subjects receiving estrogen.

The prolactin response to hypoglycemia was evaluated in 22 control subjects and 8 patients with hypothalamic-pituitary disease but normal basal serum prolactin levels. Eighteen of the 22 control subjects demonstrated at least a twofold prolactin rise in response to hypoglycemia. In contrast to the control subjects, none of the 8 patients demonstrated a prolactin response to hypoglycemia. This blunted prolactin response to hypoglycemia was the only endocrine abnormality in 3 of these 8 patients. In an attempt to better determine the sensitivity of the prolactin response to hypoglycemia as an index of early pituitary disease, the effect of a short course of estrogen on the prolactin response to hypoglycemia was examined. Estrogen was selected because of its known acute stimulatory effect on pituitary mitosis and chronic effects that lead to pituitary tumor formation in rodents. Accordingly, diethylstilbestrol (DES) 5 mg t.i.d. was administered orally to 6 normal men for 3 days, a period known to stimulate pituitary mitotic activity in rodents. Diethylstilbestrol treatment caused significant elevation of the baseline prolactin (8 +/- 2 versus 18 +/- 3 ng/ml, p less than 0.05); however, the prolactin response to hypoglycemia was blunted (8 +/- 2--30 +/- 10 ng/ml, p less than 0.05, before DES; 18 +/- 3--20 +/- 5 ng/ml after DES, p greater than 0.05). This estrogen-induced blunted prolactin response to hypoglycemia resembled the blunted prolactin response to hypoglycemia found in patients with hypothalamic-pituitary disease.

Acromegaly↗
PubMed1985

Endocrine-mediated parallel changes in hepatic glucocorticoid and prolactin receptors.

The objective of this study was to determine whether in female rat liver any relationship existed between prolactin and glucocorticoid receptors after hormonal manipulation. Bromocryptine (CB-154) treatment of adult SD female rats (80-100 days old) for 48 h decreased prolactin binding to hepatic membranes 49% and dexamethasone binding in hepatic cytosol 40% below control values. Administration of rat prolactin along with bromocriptine prevented these changes. In another study, prolactin binding to hepatic membranes increased 53% and dexamethasone binding in hepatic cytosol increased 113% above sham-control values, 3 days after adrenalectomy. On the other hand, hydrocortisone treatment of sham-operated rats reduced prolactin binding by 57% and dexamethasone binding by 76%. Scatchard analyses of the prolactin or dexamethasone binding data indicated that these manipulations changed the number of prolactin or dexamethasone binding sites rather than their apparent affinity constants. In vitro treatment of rat whole liver homogenate with various doses (10(-9) - 10(-5) M) of dexamethasone and corticosterone for 15 min at 22 degrees C resulted in a dose-dependent decrease in prolactin binding activity. However, direct addition of dexamethasone to a hepatic 15 000 X g to 100 000 X g membrane preparation exhibited no significant effects on prolactin binding. In conclusion, these studies show that (a) there is a parallel in vivo modulation of rat liver prolactin and glucocorticoid receptors under various experimental conditions and (b) in vitro exposure of whole liver homogenate to glucocorticoids inhibits the prolactin binding activity.

Adrenalectomy↗
PubMed1990

Regulation of interleukin 2-driven T-lymphocyte proliferation by prolactin.

The requirement for prolactin in interleukin 2-driven T-cell proliferation was evaluated. Addition of an anti-prolactin antiserum resulted in the specific inhibition of T-cell proliferation in a time- and dose-dependent manner. Synthesis of prolactin and its mRNA, however, did not occur during interleukin 2 stimulation. Instead, previously internalized prolactin, presumably from fetal bovine serum, appears to serve as the source of prolactin under serum-free conditions. A 7-fold increase in a prolactin receptor occurred as a function of cell cycle progression; accumulation of a 1.6-kilobase prolactin receptor mRNA increased approximately 2-fold. Interleukin 2 stimulation induced the translocation of prolactin into the nucleus and prolactin receptor to the nuclear periphery. These data indicate that extracellular prolactin is requisite for T-cell proliferation and suggest that the effects of prolactin are exerted in the nucleus.

Animals↗
PubMed2006

High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats.

High physiological prolactin induced positive calcium balance by stimulating intestinal calcium absorption, reducing renal calcium excretion, and increasing bone calcium deposition in female rats. Although prolactin-induced increase in trabecular bone calcium deposition was absent after ovariectomy, its effects on cortical bones were still controversial. The present investigation, therefore, aimed to study the effect of in vivo long-term high physiological prolactin induced by either anterior pituitary (AP) transplantation or 2.5 mg/kg prolactin injection on cortical bones in ovariectomized rats. Since the presence of prolactin receptors (PRLR) in different bones of normal adult rats has not been reported, we first determined mRNA expression of both short- and long-form PRLRs at the cortical sites (tibia and femur) and trabecular sites (calvaria and vertebrae) by using the RT-PCR. Our results showed the mRNA expression of both PRLR isoforms with predominant long form at all sites. However, high prolactin levels induced by AP transplantation in normal rats did not have any effect on the femoral bone mineral density or bone mineral content. By using (45)Ca kinetic study, 2.5 mg/kg prolactin did not alter bone formation, bone resorption, calcium deposition, and total calcium content in tibia and femur of adult ovariectomized rats. AP transplantation also had no effect on the cortical total calcium content in adult ovariectomized rats. Because previous work showed that the effects of prolactin were age dependent and could be modulated by high-calcium diet, interactions between prolactin and these two parameters were investigated. The results demonstrated that 2.0% wt/wt high-calcium diet significantly increased the tibial total calcium content in 9-wk-old young AP-grafted ovariectomized rats but decreased the tibial total calcium content in 22-wk-old adult rats. As for the vertebrae, the total calcium contents in both young and adult rats were not changed by high-calcium diet. The present results thus indicated that the adult cortical bones were potentially direct targets of prolactin. Moreover, the effects of high physiological prolactin on cortical bones were age dependent and were observed only under the modulation of high-calcium diet condition.

Animals↗
PubMed2000

Newt prolactin and its involvement in reproduction.

The amino acid sequence of newt (Cynops pyrrhogaster) prolactin deduced from the nucleotide sequence of its cDNA showed a relatively high homology with sequences of chicken and sea turtle prolactins as well as with those of anuran prolactins. Cynops prolactin receptor transcripts were detected in various tissues and organs, suggesting that prolactin plays multiple roles in urodeles. Urodele prolactin was purified from the pituitaries of C. pyrrhogaster. Antiserum against this prolactin was used for radioimmunoassay of plasma prolactin and immunoneutralization experiments. Endogenous prolactin was shown to induce migration to water, courtship behavior, and cessation of spermatocytogenesis in the Cynops newt. The hormone was found to be involved in the development of cloacal glands such as the lateral and abdominal glands, growth of the tail and Mauthner neurons, secretion of oviducal jelly, and enhanced synthesis of a female attracting pheromone (sodefrin), and responsiveness of the olfactory epithelium to sodefrin. In most of these cases, prolactin was found to act synergistically or antagonistically with sex steroids. We also discovered that hypersecretion of prolactin in the newts subjected to cold temperature was induced by hypothalamic stimulation rather than release from hypothalamic inhibition.

Amino Acid Sequence↗
PubMed1977

Prolactin binding in ovariectomy-responsive and ovariectomy-nonresponsive rat mammary carcinoma.

Growth of the transplantable mammary tumor, MTW9, in W/Fu rats is greatly enhanced by elevated serum prolactin concentrations. This report compares the prolactin binding to tumor membranes in two mammary tumor strains derived from MTW9. Maximum binding to membranes of both tumors occurred at pH 7.6 after incubation for 30 hr at 4 degrees. The binding was inhibited only by polypeptide hormones that possess lactogenic activity. MTW9-P, an ovariectomy-responsive tumor developed in rats maintained on daily perphenazine injections, had 4-fold-higher prolactin binding than had MTW9MtT, an ovariectomy-nonresponsive tumor developed in rats bearing the mammosomatotropic pituitary tumor, MtTW10. Withdrawal of perphenazine from rats bearing MTW9-P caused a fall to normal of plasma prolactin, no tumor regression, and no significant change in prolactin binding. In contrast, resection of MtT resulted in tumor regression, a fall to normal of serum prolactin, and a nearly 3-fold increase in prolactin binding. Scatchard plots of prolactin binding data yield an apparent affinity constant, Ka, of 1.2 X 109 liters/mole for both tumors. The 4-fold-higher prolactin binding in the ovariectomy responsive variant suggests a positive correlation between ovariectomy response and the number of membrane prolactin-binding sites. No correlation between prolactin sensitivity and prolacting binding is apparent.

Animals↗
PubMed1986

Effects of physiological and abnormally elevated prolactin levels on the pituitary-testicular axis.

Prolactin can influence testicular function both directly, and indirectly via altering release of gonadotropins from the pituitary. Although numerous effects of prolactin on male reproductive functions have been described, only a few were demonstrated in more than one species. These include effects on male accessory reproductive glands, on testicular luteinizing hormone receptors, on the release of gonadotropins and on sexual behavior. In rodents, prolactin appears to play a physiological role in the pituitary regulation of testicular function. This is especially pronounced in the golden hamster. In this seasonally-breeding species, alteration of prolactin release is one of the mechanisms mediating the effects of photoperiod on the testis. In the hamster, prolactin is required for the maintenance of luteinizing hormone and prolactin receptors in the testis and treatment with prolactin can completely reverse testicular atrophy induced by exposure to short photoperiod. In both men and rats, excessive release of prolactin (hyperprolactinemia) leads to suppression of sexual behavior and gonadotropin release. These effects appear to be due to the action of prolactin on the central nervous system. Most, if not all, of the effects of prolactin exhibit striking variability among species. Moreover, prolactin can exert differential effects on the same target tissue in the same species, depending primarily on the dose.

Animals↗
PubMed1996

A heterologous assay for measuring prolactin in pituitary extracts and plasma from Australian flying foxes (genus Pteropus).

A sensitive heterologous assay was developed to measure prolactin-like activity in Pteropus alecto, P. poliocephalus, and P. scapulatus, Australian flying foxes. Adapted from an established radioimmunoassay for rabbit PRL, it utilises the well-characterised, polyclonal antiserum 33/9 (guinea pig anti-human prolactin). In the assay, pituitary extracts from P. alecto, P. poliocephalus, and P. scapulatus diluted in parallel with ovine prolactin standards, although absolute levels estimated were low. Its usefulness for investigating the role of prolactin in reproduction and seasonality in flying foxes was tested. In a survey of pituitary extracts collected from both sexes of all three species, prolactin was higher in females than in males (P < 0.001). In the few specimens from juveniles, mean prolactin levels in pituitary and plasma were similar to those of adults. Plasma and pituitary samples both contained higher concentrations of prolactin during late pregnancy (P. scapulatus, plasma P < 0.01; pituitary P < 0.01) and lactation (P. poliocephalus, plasma P < 0.005; pituitary P < 0.05) in mature females. Plasma prolactin increased at about the time of parturition, but returned to nonpregnant levels rapidly if lactation was not established. In lactating females, plasma prolactin was suppressed by temporary removal of the sucking young, and was slow to recover after the young was returned to the nipple. Pharmacological responses were tested in pregnant P. poliocephalus: plasma prolactin was low following bromocriptine administration and elevated following domperidone. Prolactin is concluded to play significant roles in the reproductive physiology of female flying foxes and, as in other species, is under dopaminergic regulation.

Animals↗
PubMed1998

Cloning and sequence analysis of a pituitary prolactin cDNA from the brushtail possum (Trichosurus vulpecula).

Overlapping cDNA partial clones of pituitary prolactin from the marsupial brushtail possum (Trichosurus vulpecula) were isolated and sequenced. The nucleotide and deduced amino acid sequences showed high sequence identity with pig prolactin (84.3 and 92.5%, respectively) and all of the expected structural features of a quadruped prolactin. A prolactin gene tree was constructed and rates of evolution calculated for possum along with several mammalian and nonmammalian prolactins. Possum prolactin was most closely linked to the prolactins of eutherian mammals but branched from the main mammalian line well before the eutherian prolactins. The prolactin/GH family shows variable rates of evolution ranging from 0.3 substitutions/amino acid site/year x 10(9) for pig prolactin to 7.0 substitutions/ amino acid site/year x 10(9) for the mouse. Since divergence from the eutherian mammals, possum prolactin has shown a slow rate of evolution (0.2 substitutions/ amino acid site/year x 10(9)). As expected, the prolactin gene was expressed in the possum pituitary gland but not in the liver, lung, kidney, heart, or mammary gland.

Amino Acid Sequence↗
PubMed2001

Regulation of yolk-androgen concentrations by plasma prolactin in the American kestrel.

The concentrations of maternally derived androgens in the yolks of avian eggs vary within and among clutches, but a mechanistic basis for this variation has not been elucidated. We investigated in the American kestrel, Falco sparverius, whether changes in plasma-prolactin concentrations induced by changes in photoperiod and food supply affect yolk-androgen concentrations. Over the course of a photoinduced breeding period in the laboratory, we measured concentrations of plasma immunoreactive prolactin (ir-prolactin) in female kestrels with ad libitum food availability (control) or food availability that was reduced during the early breeding period. In a second laboratory study, we administered via osmotic mini-pumps ovine prolactin (o-prolactin) to females beginning on the day they laid their first egg of a clutch (egg-day 1) to determine the effects of high prolactin concentrations on yolk-androgen concentrations. In both this study and one on free-living kestrels, we quantified changes in yolk-androgen concentrations with date of clutch initiation. Concentrations of ir-prolactin in nonlaying females rose with date, irrespective of food treatment. Egg-day 1 ir-prolactin concentrations were higher in control females laying late during the breeding phase than in those laying early. This increase was absent in food-reduced females. Yolk-androgen concentrations in eggs 3 and 4 but not eggs 1 and 2 of the clutch were higher in clutches initiated late than in clutches initiated early in the breeding phase in both the field and laboratory. o-prolactin treatment elevated yolk-testosterone but not androstenedione concentrations. These findings suggest that, in American kestrels, seasonal and laying-associated increases in plasma-prolactin concentrations elevate yolk-testosterone concentrations. Food availability and other factors may interact with date to regulate the effects of prolactin on yolk-testosterone deposition.

Androgens↗
PubMed1988

Mammary lipoprotein lipase in plasma of cows after parturition or prolactin infusion.

Plasma lipase activity from the mammary vein and a tail blood vessel was measured in periparturient Holstein cows treated in one of three ways: control, CB154 (2-Br-alpha-ergocryptin) or CB154 plus prolactin. CB154 administration decreased basal serum prolactin concentration by 80% and blocked the normal parturient increase of serum prolactin. In CB154 plus prolactin-treated cows, prolactin was infused continuously for six days starting five and eight days prepartum. Plasma lipase activity was not detectable up to 26 hr prepartum in control and CB154-treated cows or before the start of prolactin infusion in CB154 plus prolactin-treated cows. After two hr prepartum, plasma lipase activity was detected in all treatments. In CB154 plus prolactin-treated cows, plasma lipase activity was detected in the presence of high concentrations of serum progesterone four days after the start of prolactin infusion and at least two days before parturition. Plasma lipase activity was four times greater in the mammary vein than in the tail vessel at sampling times at which activity was detected in both vessels. We propose the difference between plasma lipase activity from the mammary vein and tail vessel is due to release of lipoprotein lipase from the mammary gland into blood, and this activity can be induced prepartum by prolactin or at parturition even if the parturient increase in prolactin is suppressed.

Animals↗
PubMedDate not supplied

Serum prolactin and tumors of the prostate: unchanged basal levels and lack of correlation to serum testosterone.

To investigate the possible role of circulatory levels of prolactin on the development of prostatic tumors, and to gain insight into the prolactin-androgen relationship, serum prolactin and testosterone were determined in 73 patients with newly diagnosed prostatic adenocarcinoma. Controls consisted of 32 patients with benign prostatic hyperplasia before treatment, 19 age-matched controls, and 21 young individuals. Hormones were measured under standardized conditions by highly specific and sensitive radioimmunoassays. There was no difference in prolactin in the elderly men regardless of prostate pathology, but a significant increment was found in young controls. Individual prolactin values did not correlate with serum testosterone, and there was no statistical regression in prolactin values of patients in the age range between 50 and 80 years. In a second study, serum testosterone and prolactin were measured in 7 patients with prostate cancer and in 6 individuals with benign prostatic hyperplasia before and 30 and 60 minutes after stimulation with an iv bolus of 200 microgram TRH. Both hormones were within the normal range at time T0, and a significant stimulation of prolactin was achieved (p less than 0.001). Prolactin values did not differ between patients with benign and malignant prostatic disease. Thus, when investigating the role of prolactin in neoplastic prostatic growth in the human, it seems necessary to investigate receptor-mediated prostatic tumor responsiveness, and interferences with androgen converting enzymes on a cellular level, rather than circulating prolactin concentrations.

Adenocarcinoma↗
PubMed1983

Human myometrium: a new potential source of prolactin.

Human myometrium is shown for the first time to produce prolactin in vitro. This prolactin is similar to pituitary prolactin by criteria of immunologic identity, gel chromatography and bioassay. The de novo synthesis of myometrical prolactin is supported by no detectable prolactin in initial tissue homogenate, nondetectable prolactin production during the first 24 hours of culture, cycloheximide inhibition of prolactin production with recovery of production in control medium, and tritiated leucine incorporation into prolactin. Although human myometrium is capable of producing prolactin without the addition of exogenous hormones, the addition of estrogen and progesterone, respectively, enhances and suppresses prolactin production in contrast to decidualized human endometrium where opposite effects on prolactin production are found.

Culture Techniques↗
PubMed1988

Physicochemical characterization and functional activity of fibroid prolactin produced in cell culture.

Evidence from our laboratory with the use of cultured (primary and passaged) cells has extended our initial observation that human uterine fibroid is an extrapituitary source of prolactin. Fibroid prolactin antigen in conditioned medium reacted specifically in radioimmunoassay for human pituitary prolactin. Control experiments demonstrated that the radioimmunoassay results were not spurious due to degradation of tracer 125I-labeled prolactin. Immunoparallel dilution curves indicated antigenic relatedness of pituitary and fibroid prolactin. In a calibrated Sephadex G-100 column, fibroid prolactin eluted in the same region (20.3 to 20.9 kd) as purified pituitary prolactin. Glycosylated prolactin, detected by concanavalin A affinity column chromatography, appeared to constitute only a small percentage of fibroid prolactin made in culture. The ratio of fibroid prolactin bioactivity (lactogen Nb2 lymphoma bioassay) to antigen (radioimmunoassay) was 0.77. These data indicate that human uterine fibroid tissue produces a molecule similar to or, perhaps, identical with pituitary prolactin.

Cells, Cultured↗
PubMed1975

The clinical utility of a heterologous radioimmunoassay for human prolactin.

A specific and sensitive double antibody radioimmunoassay for human prolactin has been developed utilizing anti-human prolactin and purified ovine prolactin for radioiodination. Employing this radioimmunoassay, as little as 1.5 ng of prolactin can be quantified in a ml of human serum. The prolactin in serum detected by the radioimmunoassay behaved in a similar manner to purified human 125-I-labled prolactin on polyacrylamide gel electrophoresis. Exogenous prolactin could be completely recovered when varying amounts were added to a constant volume of serum. In normal control and primary hypothyroid subjects, intravenous administration of thyrotropin-releasing hormone elicited a peak prolactin response 30 min post-injection. Hyperthyroid and hypopituitary subjects did not manifest a significant increase in serum prolactin concentration after the injection. Subjects with functional galactorrhea had high resting prolactin levels and exhibited peak increase in serum prolactin concentration at 60 min following the administration of thyrotropin-releasing hormone.

Animals↗