The ontogenesis of human fetal hormones. III. Prolactin

Macroprolactin in mothers and their babies: what is its origin?

OBJECTIVES

Macroprolactinemia is one of the major causes of hyperprolactinemia. The aim of this study was to clarify the origin of macroprolactin (macro-PRL).

METHODS

We examined macro-PRL in the sera of 826 pregnant women and in those of their babies' umbilical cords at delivery. Macro-PRL was evaluated by precipitation with polyethylene glycol (PEG), gel filtration chromatography (GFC), and absorption with protein G (PG).

RESULTS

We detected macro-PRL in 16 out of the 826 pregnant women (1.94 %) and in 14 of their babies, which may indicate the possibility of hereditary origin of macro-PRL. However, the macro-PRL ratios of the babies correlated positively with those of their mothers (r=0.72 for GFC, p<0.001 and r=0.77 for PG, p<0.001), suggesting that the immunoglobulin (Ig)G-type anti-PRL autoantibodies might be actively transferred to babies via the placenta and form macro-PRL by binding to their babies' PRL or PRL-IgG complexes may possibly pass through the placenta. There were two cases in which only mothers had macro-PRL, indicating that the mothers had autoantibodies that did not pass through the placenta, such as IgA, PRL bound to the other proteins or PRL aggregates. No cases were found in which only the babies had macro-PRL and their mothers did not, suggesting that macro-PRL might not arise by non-hereditary congenital causes.

CONCLUSIONS

Macro-PRL in women of reproductive age might be mostly IgG-type anti-PRL autoantibody-bound PRL. The likely origin of macro-PRL in babies is the transplacental transfer of IgG-type anti-PRL autoantibodies or PRL-IgG complexes from the mothers to their babies.

Tissue concentration of aldosterone in fetal adrenals of intrauterine death cases

OBJECTIVES

Fetal adrenals are one of the main organs responsible for maturation and survival. Extant literature is not clear about whether second trimester fetal adrenals are capable of synthesizing secreting aldosterone.

METHODS

We have taken 20 adrenals from fetuses of intrauterine death cases. None of the fetuses had any external malformations and obstetric history was unremarkable. The organs were weighed and homogenized. The supernatant was used for aldosterone estimation by ELISA.

RESULTS

We consistently detected aldosterone in all the cases including second trimester. However, we did not see any correlation between aldosterone concentration and gestational age. It is striking to note that there are wide variations in the tissue levels of aldosterone across different gestational ages and also same period.

CONCLUSIONS

Tissue aldosterone levels in second trimester can be possibly induced by stress preceding intrauterine deaths. It is possible that functional status of adrenal is different in intrauterine death cases as opposed to elective abortions in second trimester.

Prolactinoma through the female life cycle

Prolactinomas are the most common secretory pituitary adenoma. They typically occur in women in the 3rd-6th decade of life and rarely in the pediatric population or after menopause. Most women present with irregular menses and/or infertility. Dopamine (DA) agonists, used in their treatment, are safe during pregnancy, but in most cases are discontinued at conception with close monitoring for signs or symptoms of tumor growth. Breastfeeding is safe postpartum, provided there was no significant growth during pregnancy. Some women will experience normalization of prolactin levels postpartum. Menopause may also decrease prolactin levels and even those with macroprolactinomas may consider discontinuing their DA agonist with close follow-up. Prolactinomas may be associated with decreased quality of life scores in women, and play a role in bone health and cardiovascular risk factors. This review discusses the current literature and clinical understanding of prolactinomas throughout the entirety of the female life cycle.

Growth hormone and prolactin regulate human neural stem cell regenerative activity

We have previously shown that the growth hormone (GH)/prolactin (PRL) axis has a significant role in regulating neuroprotective and/or neurorestorative mechanisms in the brain and that these effects are mediated, at least partly, via actions on neural stem cells (NSCs). Here, using NSCs with properties of neurogenic radial glia derived from fetal human forebrains, we show that exogenously applied GH and PRL promote the proliferation of NSCs in the absence of epidermal growth factor or basic fibroblast growth factor. When applied to differentiating NSCs, they both induce neuronal progenitor proliferation, but only PRL has proliferative effects on glial progenitors. Both GH and PRL also promote NSC migration, particularly at higher concentrations. Since human GH activates both GH and PRL receptors, we hypothesized that at least some of these effects may be mediated via the latter. Migration studies using receptor-specific antagonists confirmed that GH signals via the PRL receptor promote migration. Mechanisms of receptor signaling in NSC proliferation, however, remain to be elucidated. In summary, GH and PRL have complex stimulatory and modulatory effects on NSC activity and as such may have a role in injury-related recovery processes in the brain.

What can we learn from rodents about prolactin in humans?

Prolactin (PRL) is a 23-kDa protein hormone that binds to a single-span membrane receptor, a member of the cytokine receptor superfamily, and exerts its action via several interacting signaling pathways. PRL is a multifunctional hormone that affects multiple reproductive and metabolic functions and is also involved in tumorigenicity. In addition to being a classical pituitary hormone, PRL in humans is produced by many tissues throughout the body where it acts as a cytokine. The objective of this review is to compare and contrast multiple aspects of PRL, from structure to regulation, and from physiology to pathology in rats, mice, and humans. At each juncture, questions are raised whether, or to what extent, data from rodents are relevant to PRL homeostasis in humans. Most current knowledge on PRL has been obtained from studies with rats and, more recently, from the use of transgenic mice. Although this information is indispensable for understanding PRL in human health and disease, there is sufficient disparity in the control of the production, distribution, and physiological functions of PRL among these species to warrant careful and judicial extrapolation to humans.

Paracrine/autocrine control of female reproduction

Neuropeptides, growth factors and cytokines are expressed in reproductive organs and tissues, where they interact with afferent endocrine messages to modulate cell proliferation and differentiation, local hormone secretion and vascular function. These events regulate complex processes such as gonadotropin pulsatility, ovulation, implantation and parturition. During reproductive life, a number of neuropeptides produced within the hypothalamus play a modulatory role in the control of gonadotropin-releasing hormone (GnRH) release, hence characterizing a hypothalamic paracrine system. The pituitary gland is a source and target of inhibin-related proteins, and these typical 'gonadal' products, once secreted by the pituitary cells, acquire the function of paracrine modulators of follicle-stimulating hormone (FSH) secretion. In the ovary, the effect of gonadotropins is locally modulated by growth factors acting in an autocrine/paracrine manner, although their precise role in folliculogenesis remains uncertain. Numerous local factors are involved in the control of endometrial growth, differentiation, receptivity and menstruation. Alterations in the paracrine endometrial system may underlie pathological processes such as infertility or endometrial neoplasia. The human placenta and its related membranes produce cytokines, hormones and growth factors that participate in the control of gestational development as well as in the maternal-fetal adaptation to gestational diseases. There is increasing evidence that paracrine signaling plays a fundamental role in all spheres of female reproductive function, and future research will concentrate on clarifying which of these local mechanisms play a decisive role in both physiology and disease, thus giving rise to new therapeutic strategies.

Circulating levels of growth hormone, insulin-like growth factor-I and prolactin in normal, growth retarded and anencephalic human fetuses

We measured growth hormone (GH), insulin-like growth factor-I (IGF-I), and both total and glycosylated prolactin (PRL) levels in 131 blood samples obtained by cordocentesis in normal and abnormal fetuses from 19 to 40 weeks of gestation. In normal fetuses, IGF-I and PRL levels showed a positive correlation and GH a negative correlation with gestational age. A negative relation between GH and IGF-I levels was observed, while PRL did not show any correlation with both GH and IGF-I concentrations. IGF-I increased from 5.6 +/- 3 (at 19-22 weeks) to 10.7 +/- 5 nmol/l at term; GH decreased from 31 +/- 10 to 7.7 +/- 4 micrograms/l and PRL increased from 16 +/- 18 to 139 +/- 76 micrograms/l. Glycosylated PRL accounted for about 15% of total PRL, a value similar to that found in normal adults. In 27 fetuses of 27-37 weeks with intra-uterine growth retardation, GH and PRL levels were higher and IGF-I levels lower than in normal fetuses matched for week of gestation. In 8 anencephalic fetuses of 19-26 weeks of gestation, both GH and IGF-I levels were lower, and PRL levels were higher than in matched controls. Altogether these data support the views that a) both GH and PRL secretion are under the hypothalamic control during fetal development, b) the serum GH decrease from midgestation to the end of pregnancy is mediated by the negative feed-back mechanism of increasing IGF-I levels and c) IGF-I production is mainly regulated by fuel supply and only partially by GH.

Serum prolactin concentration in normal and small for gestational age fetuses

OBJECTIVES

To study fetal and maternal serum prolactin concentrations in appropriately-grown (AGA) fetuses and in small for gestational age (SGA) fetuses.

DESIGN

A cross-sectional study of 27 AGA and 27 SGA fetuses undergoing cordocentesis for prenatal diagnosis or for determination of fetal karyotype and acid-base balance. Serum prolactin concentration was measured by radioimmunoassay.

SETTING

Harris Birthright Research Centre for Fetal Medicine.

RESULTS

In the AGA group, both fetal and maternal serum prolactin concentration increased significantly with gestation (P < 0.001 and P < 0.01, respectively). In the SGA group, the fetal concentration of prolactin was significantly higher (P < 0.05), but the maternal serum prolactin concentration was not different from that of the AGA group.

CONCLUSIONS

The finding of prolactin in the fetal circulation suggests that the anterior lobe of the pituitary is functioning from at least 12 weeks gestation. The increased serum prolactin concentration in SGA fetuses may be the consequence of hypoglycemic stress on the pituitary or the relative immaturity of the inhibitory hypothalamic-pituitary pathways.

Plasma prolactin and clinical outcome in preterm infants

Plasma prolactin was measured weekly in 280 preterm infants. The complex gestational age dependent pattern of postnatal prolactin release has been defined and reference standards provided. Plasma prolactin was higher in girls, with increasing divergence between the sexes from the third week onwards, and higher after two weeks, in infants of mothers with pregnancy related hypertension. Diet, assigned randomly, exerted a major effect on plasma prolactin, with significantly higher values in infants fed donor breast milk or standard formula than in those fed a protein, energy, and mineral enriched preterm formula. After adjusting for confounding factors, infants with the lowest plasma prolactin concentrations (less than 1000 mU/l, 32.9 micrograms/l) occurring usually at a nadir between days 5 and 12, showed a 120% increase in the duration of ventilatory assistance required, a 20% increase in the number of days to attain full enteral feeds, and a 30% decrease in length gain. We suggest preterm birth disrupts the normal perinatal pattern of prolactin release and that those infants who develop relatively low plasma concentration have an adverse outcome. Our data add to the broader debate on whether preterm infants require multiple endocrine replacement treatment.

Hormonal and developmental regulation of pulmonary surfactant synthesis in fetal lung

Pulmonary surfactant, a unique developmentally regulated, phospholipid-rich lipoprotein, is synthesized by the type II cells of the pulmonary alveolus, where it is stored in organelles termed lamellar bodies. The principal surface-active component of surfactant, dipalmitoylphosphatidylcholine, a disaturated form of phosphatidylcholine, acts in concert with the surfactant-associated proteins to reduce alveolar surface tension. Relatively large amounts of phosphatidylglycerol also are present in lung surfactants of a number of species, including man. The role of phosphatidylglycerol in surfactant function has not been elucidated; however, its presence in increased amounts in pulmonary surfactant is correlated with enhanced fetal lung maturity. Surfactant glycerophospholipid synthesis in fetal lung tissue is regulated by a number of hormones and factors, including glucocorticoids, prolactin, insulin, oestrogens, androgens, thyroid hormones, and catecholamines acting through cyclic AMP. In studies with human fetal lung in organ culture, we have observed that glucocorticoids, in combination with prolactin and/or insulin, increase the rate of lamellar body phosphatidylcholine synthesis and alter lamellar body glycerophospholipid composition to one reflective of surfactant secreted by the human fetal lung at term. Four surfactant-associated proteins, SP-A, SP-B, SP-C and SP-D, have recently been characterized. Recognition of their potential importance in the reduction of alveolar surface tension and in endocytosis and reutilization of secreted surfactant by type II cells has stimulated rapid advancement of knowledge concerning the structures of the surfactant proteins and their genes, as well as their developmental and hormonal regulation in fetal lung tissue. The genes encoding SP-A, SP-B and SP-C are expressed in a cell-specific manner and are independently regulated in fetal lung tissue during development. SP-A gene expression occurs exclusively in the type II cell and is initiated after 75% of gestation is complete. In the human fetus, expression of the SP-B and SP-C genes is detectable much earlier in development than SP-A, before the time of appearance of differentiated type II cells. It is apparent from studies using human and rabbit fetal lung in culture that cyclic AMP and glucocorticoids serve important roles in the regulation of SP-A gene expression. While the effects of cyclic AMP are exerted primarily at the level of gene transcription in human fetal lung tissue, glucocorticoids have stimulatory effects on SP-A gene transcription and inhibitory effects on SP-A mRNA stability. In addition, cyclic AMP and glucocorticoids act synergistically to increase SP-A gene transcription in human fetal lung in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)

Maternal and fetal prolactin in pregnancy-induced hypertension

In plasma from 35 women with pregnancy-induced hypertension (PIH) and 35 normal pregnant women both at 39 weeks of gestation, plasma prolactin levels were measured at 8.30 a.m. (PRL1) and 9.30 a.m. (PRL2) under basal conditions. At delivery umbilical cord blood samples were taken for measurement of fetal prolactin (PRLF). PRL1 and PRL2 were higher in women with PIH, but no significant relations were found between PRL1/PRL2 and blood pressure. PRLF did not differ when infants of mothers with PIH and infants of normal pregnant women were compared, but PRLF had a significant direct independent relation with PRL2. The latter relation may be due to the increase in placental oestrogens during pregnancy, which stimulate both the maternal and fetal hypophyses and their prolactin secretion. PRLF did not show any relation with neonatal morbidity, but PRL1 showed a significant direct relation with the Apgar score at 5 min.

The effect of labour on prolactin and cortisol concentrations in the mother and the fetus

Concentrations of prolactin and cortisol were determined in maternal and umbilical cord serum of women delivered by elective Caesarean section and by vaginal delivery. There was no difference in the concentration of prolactin in the two groups of women. Similarly, cord blood prolactin concentrations were not significantly different in the two groups. Cortisol concentrations in the women undergoing Caesarean section were similar to the vaginal delivery group before the onset of labour. However, there was a significant increase in cortisol concentration at delivery following labour. The cord blood cortisol concentration was significantly higher in the neonates delivered vaginally, and it correlated with the maternal cortisol concentration at delivery. The relevance of these findings is discussed.

Drug-induced changes in prolactin secretion. Clinical implications

Prolactin secretion is affected by various diseases as well as by many drugs in humans and animals. While marked hyperprolactinaemia suggests the presence of a pituitary tumor, moderate changes may also occur in various endocrine or non-endocrine disorders. Drugs can interfere with prolactin regulation via complex mechanisms at the hypothalamus or at the pituitary site, but possible changes in prolactin metabolism are poorly understood as yet. This survey of the literature up to June 1986 covers the influence of various groups of drugs and agents on the plasma prolactin level under various conditions. It contains information that will facilitate evaluation of whether hyper- or hypoprolactinaemia may result from therapeutic intervention or must be related to an underlying disease. It is obvious that more subtle changes can be revealed by the use of dynamic tests either to stimulate or to suppress prolactin secretion.

Hyperprolactinaemia in congenital hypothyroidism

Serum prolactin concentrations were measured in nine untreated hypothyroid infants and 23 euthyroid controls. In the former group the serum prolactin concentrations were tenfold higher than the controls (352 vs 34 micrograms/l), declining gradually upon treatment. Although serum prolactin concentrations can be mildly elevated in adults with hypothyroidism, congenital hypothyroidism causes a profound and probably uniform hyperprolactinaemia; furthermore, the hormone concentration correlates directly with the simultaneous TSH concentration. The physiological importance, if any, of the hyperprolactinaemia in the fetus or neonate is uncertain.

Sexual maturation of the hypothalamus: pathophysiological aspects and clinical implications

Sexual maturation in humans begins early in fetal life and culminates in adulthood when the gonads have acquired a full capacity for reproduction. It is remarkable that during this long process, the pituitary gonadal function, hence its hypothalamic control presents an alternative of activation and inhibition periods, during which the interrelations of the 3 components of the hypothalamic-pituitary-gonadal axis change gradually and inversely. The ontogeny of the hypothalamic-pituitary system, the varying activity of the reproductive endocrine system throughout sexual maturation and the developmental changes in the interrelations of the hypothalamic-pituitary-gonadal axis are reviewed: the most striking feature of human sexual development is the long inhibition of hypothalamo-pituitary function during childhood. Much indirect evidence points to the determining role of the CNS in the maturation of hypothalamic function: the occurrence of rhythms of secretion, the amplitude of secretions and peripubertal specific sleep-related nycthemeral rhythm of secretion at the onset of puberty. Despite the reality of a negative feedback control, these changes do occur independently of gonadal secretions since they are observed (qualitatively if not strictly quantitatively) in agonadal children. It is likely that neurotransmitters (dopamine, serotonine) and opiates have an inhibitory effect on Gn-RH release. But we still don't know their evolution during sexual maturation. It does not appear that melatonine plays any determinant role in the onset of human puberty. The clinical implications of our present understanding of the physiological events occurring during sexual maturation are several. Considering the major problems related to abnormal sexual maturation we will discuss successively: (1) diagnosis of hypogonadotrophic hypogonadism in early infancy; (2) differential diagnosis between premature thelarche and true sexual precocity; (3) the usefulness of endocrine investigations in the evaluation of hypothalamic-pituitary function; and (4) the new developments in the treatment of precocious puberty, delayed puberty or hypogonadism.

Prolactin binding in the developing rat fetal liver

The binding of prolactin by fetal rat liver cell membrane fractions from 17 to 21 days gestation was studied. Particulate liver membranes were prepared in Dulbecco's Phosphate Buffered Saline (PBS) by ultracentrifugation and incubated at 22 degrees C for 16 hours with [125I] iodo-human growth hormone (hGH). Non-specific binding was assessed by parallel incubations in the presence of a 2000-fold excess ovine prolactin. Specific prolactin binding sites were detected only at 21 days gestation (2932 +/- 401 cpm/mg protein) in freshly prepared membranes. On freezing at -20 degrees C for 24 to 48 hours, the membranes of 20 days gestation animals were able to specifically bind prolactin (1295 +/- 239 cpm/mg protein). Freezing led to a 45 +/- 7% increase (4270 +/- 701 cpm/mg protein) in prolactin binding at 21 days gestation. No hormonal binding was detected from 17 through 19 days gestation in either fresh or freeze-thawed membranes. Scatchard analysis revealed a high affinity binding site with a Ka of approximately 1.4 X 10(8)M-1 in both fresh and freeze-thawed membrane preparations. The data show that 1) prolactin receptors appear in liver only during late fetal life and that 2) freezing of membranes may unmask binding sites that are initially unavailable to specifically bind prolactin.

Effects of an antenatal load of pyridoxine (vitamin B6) on the blood oxygen affinity and prolactin levels in newborn infants and their mothers

The effects of a loading dose of pyridoxine (100 mg) given intramuscularly or per os to 24 earlier non-supplemented pregnant women at term was investigated. The in vitro oxygen affinity (P50) and the prolactin level in both maternal and newborn blood was sampled. The blood P50 values were measured by a variant of "mixing method". Blood prolactin levels were determined by RIA. After pyridoxine administration, the maternal P50 values increased moderately and the newborns' cord blood P50 values increased significantly when compared with the control group's (number of cases 12) values. The decrease of blood oxygen affinity was most pronounced in the supplemented groups in newborns' capillary blood at the age of five days. The pyridoxine supplementation had no effect on the maternal and the newborns' cord blood prolactin level or on the daily amount of breast milk. Pyridoxine supplementation of the mother at labour may influence favourably the oxygen transport function of the newborn's blood and it may be especially advantageous in early postnatal adaptation disturbances of newborns.

Effect of metoclopramide on maternal and fetal hyperprolactinemia

To investigate the effect of metoclopramide (MET), a dopaminergic antagonist drug, on serum PRL concentration in maternal and cord blood (CB) serum, the drug was injected in 94 at term pregnant women whereas 28 mothers received saline. Maternal serum (MS) samples were obtained before MET injection and at the parturition time. According to the interval of time between MET administration and birth, MS specimens were grouped in 7 groups. CB was obtained from neonates whose mothers were injected with saline, group 0 and from newborns whose mothers were treated with MET, groups 1 to 7. In the 7 groups of women the mean PRL concentration before MET ranged between 307 and 439 ng/ml. After MET injection a significant increase has been observed in all groups with a minimum and maximal mean value of 639 and 931 ng/ml. The highest net increment of PRL has been measured in group 1 sampled at 5 to 30 minutes after MET. CB PRL concentration in group 0, saline treated, was not different from the values measured in group 1 to 7, treated groups, with a range between 504 and 703 ng/ml. These findings suggest that maternal lactotropes are still responsive to MET. On the opposite, fetal pituitary does not release PRL after MET injection probably because PRL secretory activity is maximal or because the dopaminergic receptors' system is still immature.

Placental transfer and hormonal effects of metoclopramide

In order to study the transplacental transfer of metoclopramide, and its endocrine effects, measurements were made of its concentration in maternal and fetal blood, and in the amniotic fluid, together with maternal and fetal plasma concentrations of prolactin, TSH and oestradiol, during delivery by selective Caesarean section. The drug, 10 mg, was injected i.m. 12 and 2 h and just before the onset of anaesthesia. Metoclopramide was detectable in all the umbilical arterial and venous and amniotic fluid samples, in mean concentrations of 50, 63 and 75 ng/ml, respectively. The mean ratio between the umbilical venous and maternal plasma concentrations was 0.63. Accurate maternal plasma half-lives could not be established but they must have averaged 2 to 4 h. The high amniotic fluid concentrations and relatively high umbilical venous and arterial concentrations soon after administration suggest that metoclopramide equilibrates relatively rapidly between the mother and fetus. Metoclopramide raised the maternal plasma prolactin levels from 315 +/- 128 ng/ml (SD) before therapy to 357 +/- 112 ng/ml at the time birth. No statistically significant difference in cord arterial or venous plasma prolactin levels was seen between the control and metoclopramide-treated groups. Metoclopramide did not affect maternal plasma TSH or oestradiol levels. The only change was a slight but significant increase in TSH level in cord blood taken from the umbilical artery after metoclopramide treatment.

Appearance of LH-immunoreactive cells in the Rathke's pouch of the chicken embryo

The differentiation of the pituitary of the chicken embryo was studied by means of an immunohistochemical technique using antisera to turkey and chicken pituitary hormones. Immunoreactive LH-cells are detected in 4-day embryos (stage 23 of Hamburger and Hamilton) when the primordium of the anterior pituitary, the Rathke's pouch is only composed of a single-layer epithelium lined with an undifferentiated mesenchyme. A few immunoreactive cells are observed grouped on the posterior aspect of the pouch. As development proceeds, a strip of positive cells is detected encircling the Rathke's pouch. Prolactin-, growth hormone-, and ACTH-immunoreactive cells are detected in 6- and 7-day embryos, only after the pituitary has acquired its characteristic structure with cords in which different cell types become progressively recognizable. The early appearance of immunoreactive LH-cells following a precise distribution shows that secretory properties and differentiation capacities are acquired simultaneously in the epithelium of the Rathke's pouch and may be induced by the same stimulus.

Prolactin, maternal oestrogens, and breast development in the newborn

To investigate the influence of maternal oestrogens on the fetal breast development, maternal urinary oestriol excretion, maternal plasma oestriol concentrations, and cord venous plasma oestradiol and oestriol concentrations were related to the size of the neonatal breast. A significant positive association between oestriol excretion and neonatal breast size was demonstrated, but the relationship was not strong and might be due to both measures having a positive relationship with birthweight. The infants' circulating concentrations of prolactin at birth and during the first weeks of life were also related to breast size. There was no cord venous-arterial difference in prolactin concentrations, and neither related to breast diameter. However there was a strong association between breast size and prolactin concentrations in mature infants aged between 5 and 7 days. In preterm infants breast tissue often develops after birth. Prolactin levels in preterm infants were higher between 2 and 6 weeks than they were in the first week of life. It would appear that the early development of the breast is influenced more by the infants's than the mother's endocrine activity.

Phospholipids of the lung in normal, toxic, and diseased states

The highly pulmonary concentration of 1,2-dipalmitoyl-sn-glycerol-3-phosphorylcholine (dipalmitoyllecithin) and its implication as an important component of lung surfactant have promoted investigation of phospholipid metabolism in the lung. This review will set the contents including recent informations for better understanding of phospholipid metabolism of the lung in normal state (physiological significances of lung phospholipids, characteristics of phospholipids in lung tissue and alveolar washing, biosynthetic pathways of dipalmitoyllecithin, etc.) as well as in toxic states (pulmonary oxygen toxicity, etc.) and in diseased states (idiopathic respiratory distress syndrome, pulmonary alveolar proteinosis, etc.) Since our main concern has been to clarify the most important route for supplying dipalmitoyllecithin, this review will be focused upon the various biosynthetic pathways leading to the formation of different molecular species of lecithin and their potential significance in the normal, toxic, and diseased lungs.

Prolactin deficiency, obesity, and enlarged testes--a new syndrome?

A 4-year-old boy is described who was obese and slightly mentally retarded. His testes were enlarged. The only endocrine disorder present was a failure to increase plasma prolactin after stimulation.

Relationship of newborn serum prolactin levels to the respiratory distress syndrome and maternal hypertension

Prolactin concentrations were measured in mixed cord blood of 782 newborn infants and related to the occurrence of the respiratory distress syndrome (RDS) and maternal cardiovascular condition. Infants of 30 to 33 weeks' gestational age who developed RDS had significantly lower serum concentrations of prolactin than non-RDS infants within this same age range. No difference was observed between RDS and non-RDS infants at 34 to 36 weeks. Prolactin levels in infants delivered by preeclamptic women were greater than the levels in infants of normotensive women from 30 to 39 weeks' gestation. The levels were higher in the 40 to 42 weeks age group as well; however, the difference was not statistically significant. Infants of mothers with gestational hypertension also tended to have elevated serum prolactin concentrations. No differences were observed in infants of women presenting with a history of chronic hypertension. Within the RDS subgroups, serum prolactin levels were significantly greater in infants of preeclamptic women than in infants of normotensive women, being approximately equal to the levels in the non-RDS normotensive group.

The effects of prolactin on pulmonary maturation in the fetal rabbit

The effect of ovine prolactin administration on the fetal rabbit pulmonary pressure volume relationship was determined. Using pentobarbital anesthesia, on Day 24 of gestation, a midline incision on the maternal abdomen was made to expose the bicornuate uterus. Fetal rabbits in one horn of the uterus were injected intramuscularly with a dose of 1.0 mg (0.05 ml) of prolactin solution. Similarly, fetuses in the opposite horn were administered an equivalent volume of control vehicle. On Day 26 of gestation, no significant enhancement of lung maturation, as judged from the pressure volume relationship, was found to result from prolactin administration. These results suggest that prolactin does not initiate the secretion of surface active material into the alveolar lumen of the fetal lung in sufficient amounts to induce physiologic maturation of the rabbit fetal lung.

Influence of bromocriptine on plasma levels of prolactin and steroid hormones in the 20th week of pregnancy

The influence of bromocriptine, a prolactin antagonist, on maternal plasma and amniotic fluid prolactin (PRL) was investigated in two pregnancies at the 20th week with medical indication for abortion. Voluntary consensus of the patients was obtained. Blood sample determinations demonstrated that bromocriptine inhibits the secretion of PRL both in plasma and amniotic fluid. Since no changes were observed in peripheral maternal steroid concentrations of dehydroepiandrosterone, dehydroepiandrosterone-sulfate, delta 4-androstene-3, 17-dione, testosterone, estradiol, estriol, and cortisol, it is concluded that PRL does not seem to affect maternal and fetal adrenal cortex as supposed in amenorrhoic patients with hyperprolactinemia.

Prolactin in umbilical cord blood and the respiratory distress syndrome

Prolactin was measured in umbilical cord serum obtained from 77 newborn infants of gestational age 28 to 40 weeks. A positive correlation with gestational age was demonstrated. Between 30 and 36 weeks of gestation the elevation of the regression line of the concentration of cord PRL versus gestation age was significantly lower (P less than 0.05) for those infants who developed respiratory distress syndrome compared to the regression line for infants who did not develop RDS. Between 32 and 33.5 weeks, the mean +/- SEM cord PRL concentration in infants who developed RDS (101.7 +/- 9.5 ng/ml) was significantly less (P less than 0.025) than the PRL concentration in those who did not develop RDS (161.8 +/- 18.9 ng/ml). Cord PRL did not correlate with cord cortisol or dehydroepiandrosterone sulfate concentrations. Cord growth hormone concentrations did not show any relationship to the occurrence of RDS. Serum PRL was not suppressed in a further 114 infants whose mothers were treated prenatally with betamethasone. These findings raise the possibility of a role of PRL in fetal lung maturation.

Failure to detect an effect of prolactin on pulmonary surfactant and adrenal steroids in fetal sheep and rabbits

Recent reports have indicated an association between low cord prolactin (PRL) and the occurrence of respiratory distress syndrome in premature infants, and it is reported that PRL administration increases the lecithin content of fetal rabbit lung. We administered 1 mg ovine PRL to 32 rabbit fetuses on day 24 of gestation and evaluated lung phospholipid synthesis and content on day 26. Compared with diluent-injected littermates, PRL had no effect on the rate of choline incorporation into lecithin, tissue content of phospholipid and disaturated lecithin, or plasma corticoids. However, both choline incorporation and corticoids were increased in all animals undergoing surgery compared with unoperated controls. We also infused PRL (1 mg/day, i.v.) into three fetal sheep continuously over five periods of 5-8 days. Although supraphysiologic concentrations of PRL were achieved in plasma and amniotic fluid, there was no effect of this treatment on the flux of tracheal fluid surfactant or on plasma concentrations of corticoids of dehydroepiandrosterone sulfate. Thus, in this study, we failed to detect either a stimulation of the surfactant system or an adreno-corticotropic effect by PRL as previously postulated. This suggests that the relationship between PRL and respiratory distress sundrome is an indirect association.

Hypothesis: placental membranes produce prolactin

Orthodox views for the origin of the high concentration of prolactin (PRL) present in amniotic fluid suggest it is derived from maternal or fetal serum. However, the data on which these conclusions are based can also be interpreted to indicate that this hormone may be a product of placental or periplacental tissues. Trophoblast or amnion do not appear to produce PRL, while PRL synthesis by decidua-chorion is suggested from experiments in the rhesus monkey and by in vitro incubation of human tissue. Production of PRL by an extrapituitary cell is not without precedent and would be a simple explanation for high amniotic fluid PRL concentrations. Moreover, decidual-chorionic PRL would be strategically placed to mediate local functions of this hormone such as osmoregulation and myometrial inhibition.

The effect of prolactin on the lecithin content of fetal rabbit lung

1 mg ovine prolactin was injected intramuscularly into rabbit fetuses (24th day of gestation) located in one of the two uterine horns exposed by laparotomy (n = 12). Fetuses in the other uterine horn were injected with an identical volume of vector and served as controls (n = 13). 2 days later the fetuses were removed by a second laparotomy and sacrificed. Analysis of lung tissue composition yielded the following results: (a) the prolactin-treated group of fetuses showed 40% higher total lung phospholipid content (17.0 +/- 0.8 micronmol/g) than the control group (12.2 +/- 0.5 micronmol/g); (b) the prolactin-treated group had a 67% higher lung lecithin content (8.7 +/- 0.8 micronmol/g) than the control group (5.2 +/- 0.4 micronmol/g); (c) dipalmitoyllecithin accounted for 67% of total lung lecithin in the prolactin-treated group and 44% in the control group. These differences were statistically highly significant (P less than 0.001). However, between the prolactin-treated and the control groups, there were no statistically significant differences in body weight and length, lung weight, the ratio of lung weight to body weight, DNA, protein and, water content. These results suggest that prolactin might be a trigger of lung surfactant synthesis in the rabbit fetus.

Bromocriptine for induction of ovulation in normoprolactinaemic post-pill anovulation

19 women with anovulation after discontinuing oral contraceptive agents and with normal plasma-prolactin concentrations were treated with bromocriptine. Ovulation and menstruation were restored in 9 of the 13 amenorrhoeic and 5 of the 6 oligomenorrhoeic patients. The success-rate (74%) indicates that bromocriptine is an effective treatment for post-pill anovulation in normoprolactinaemic women.

Prolactin

Prolactin exists in man as a distinct and separate anterior pituitary hormone from growth hormone. It is important in lactation and the control of gonadal function, although it may have a much wider and basic metabolic role, similar to its role in lower forms. In clinical endocrinology it is important as an index of pituitary and hypothalamic diseases; thus prolactin levels are elevated in association with these conditions and this reflects the normal tonic inhibitory hypothalamic control of prolactin by PIF; DA is the most important PIF. Hyperprolactinaemia causes hypogonadism in both men and women; it may present in women with amenorrhoea, oligomenorrhoea, polymenorrhoea, regular cycles with anovulation or a defective luteal phase, and impotence in men. In either sex galactorrhoea is reported to occur in only 30 per cent of patients. Neurotransmitter therapy, with dopamine agonists which act as functional analogues of PIF, restores prolactin levels to normal and leads to a return of normal gonadal function. The mechanism of the hypogonadism is not clear and is discussed together with the problems associated with inducing pregnancy in these patients, who may harbour microadenomata of the pituitary.

An immunocytochemical study of human pituitary mammotropes from fetal life to old age

The objectives were to (a) describe the cytology and distribution of mammotropes in the human pituitary gland, (b) determine whether the mammotrope is a distinctive secretory cell type and (c) ascertain when it first appears in the fetal hypophysis. Identification of mammotropes was based primarily on the Sternberger peroxidase-antiperoxidase immunocytochemical method used with an antiserum to human prolactin. Hypophyses from 25 male and 6 female adults, and 21 fetuses ranging in gestational age from 6 to 23 weeks were studied. In the adult two morphological forms of mammotropes were observed. Mammotrope I possessed a small perikaryon that commonly was located centrally in parenchymal cell cords. From the perikaryon long cytoplasmic processes extended toward neighboring capillaries. Mammotrope I reached its highest incidence in the posterolateral zones of the pars distalis. Mammotrope II possessed a larger perikaryon with short processes; cells of this form were fewer and occurred chiefly in the anteromedian zone. Mammotropes with intermediate morphological features that prevented classification into categories I or II were common in some hypophyses. Both forms of mammotropes were present prepuberally (one 6-week and one 9-year-old male) and in adult males and females. Mammotropes were only slightly more prominent in females than males. Regression of mammotropes was evident in old age. Mammotropes were distinctly different from somatotropes, corticotropes, gonadotropes and thyrotropes. In the fetal hypophysis mammotropes appeared first at 14 weeks of gestational age and remaind few through 16.5 weeks. Their number increased greatly at 23 weeks.

Serum thyrotropin, prolactin, and growth hormone levels during the early neonatal period in the human infant

Normal term newborn infants have been studied during the first four hours after birth. Cord blood and brachial venous blood samples were collected for measurement of serum prolactin (n = 15; 11 vaginal delivery; four cesarean section delivery), thyrotropin (n=8), growth hormone (n=7), tri-iodothyronine (n=7) and thyroxine (n=7). The mean cord serum TSH concentration was 12 +/- 2 muU/ml and peaked in all infants 30 minutes after birth (67 +/- 7 muU/ml). Blood PRL also increased in all of the 15 infants studied; the mean cord blood value of 165 +/- 15 ng/ml increased significantly to a mean of 214 +/- 22 ng/ml at 30 minutes and 204 +/- 17 ng/ml at 60 minutes. The peak blood PRL concentration was observed at 30 minutes in eight newborn infants, at 60 minutes in three, and at 120 minutes in four. Mean serum GH concentrations were statistically similar during the first four hours but there was a tendency for serum levels to fall somewhat during the first hour after birth. The mean cord serum T3 concentration (47 +/- 5 mug/ml) increased significantly to a peak value of 227 +/- 38 ng/dl at 120 minutes. The increase in T4 from a mean of 15.3 +/- 1.2 mug/dl to a mean of 17.9 +/- 2.6 mug/dl at four hours was less dramatic. These data are consistent with the possibility that the same mechanism responsible for the neonatal TSH surge may be responsible for a significant but lesser PRL surge during the early minutes after birth.

Congenital hypopituitarism associated with neonatal hypoglycemia and microphallus: four cases secondary to hypothalamic hormone deficiencies

The association of hypoglycemia and microphallus in the male neonate is presumptive evidence of congenital hypopituitarism. This was observed in four male infants with normal birth weight and length, optic discs, and intelligence, and without gross central nervous system malformations. Plasma and urinary cortisol values were low. Stimulation with metyrapone and insulin hypoglycemia failed to elicit a rise in plasma corticoids, but multiple doses of ACTH evoked a response. Growth hormone responses to arginine, insulin, sleep, L-dopa, and glucagon were uniformly less than 2.5 ng/ml. In three patients, however, length remained within 2 SD of the mean until two years of age; in one, there was a sharp decrease in growth by three months. Two patients had low plasma TSH and thyroxine concentrations within the first month of life. In the other two patients, whose thyroxine levels were measurable, intravenous administration of thyrotropin-releasing factor evoked a normal rise in plasma TSH; serum thyroxine decreased into the hypothyroid range in one after GH therapy was initiated. Plasma prolactin was normal in the first two patients receiving thyroxine replacement therapy. The other two patients had elevated baseline prolactin levels and had an augmented rise in plasma prolactin after administration of TRF. Human chorionic gonadotropin induced a 10- to 15-fold rise in plasma testosterone in the two patients tested. The changes in plasma FSH and LH after luteinizing hormone-releasing factor were either low or in the prepubertal range. In three patients, treated with testosterone enanthate intramuscularly, phallic growth occurred. In addition, all three had a transient increase in height but no acceleration of skeletal maturation. The data suggest a deficiency of hypothalamic hypophysiotropic hormones rather than a primary pituitary defect. Early recognition of this syndrome complex is critical for prompt treatment of the life-threatening cortisol deficiency. The diagnosis is more difficult in affected females because their external genitals are normal. The microphallus is a remediable manifestation of hypopituitarism.