High sodium intake is associated with increased glucocorticoid production, insulin resistance and metabolic syndrome.

OBJECTIVE: High sodium (HS) diet is associated with hypertension (HT) and insulin resistance (IR). We evaluated whether HS diet was associated with a dysregulation of cortisol production and metabolic syndrome (MetS). PATIENTS AND MEASUREMENTS: We recruited 370 adults (18-85 years, BMI 29·3 ± 4·4 kg/m(2) , 70% women, 72% HT, 61% MetS). HS diet (urinary sodium >150 mEq/day) was observed in 70% of subjects. We measured plasma hormones, lipid profile, urinary free cortisol (UFC) and cortisol tetrahydrometabolites (THM). RESULTS: Urinary sodium was correlated with UFC (r = +0·45, P < 0·001), cortisol THM (r = +0·41, P < 0·001) and inversely with adiponectin, HDL and aldosterone, after adjusting by age, gender and BMI. Subjects with high, compared with adequate sodium intake (50-149 mEq/day) had higher UFC (P < 0·001), THM (P < 0·001), HOMA-IR (P = 0·04), HT (81% vs 50%, P < 0·001), MetS (69% vs 41%, P < 0·001) and lower adiponectin (P = 0·003). A multivariate predictive model adjusted by confounders showed a high discriminative capacity for MetS (ROC curve 0·878) using four clinical variables: HS intake [OR = 5·6 (CI 2·3-15·3)], HOMA-IR [OR 1·7 (1·3-2·2)] cortisol THM [OR 1·2 (1·1-1·4)] and adiponectin [OR = 0·9 (0·8-0·9)], the latter had a protective effect. CONCLUSIONS: High sodium diet was associated with increased urinary cortisol and its metabolites. Also, HS diet was associated with HT, insulin resistance, dyslipidaemia and hypoadiponectinaemia, even when adjusting by confounding variables. Further, we observed that high salt intake, IR and higher cortisol metabolites, alone or combined in a clinical simple model, accurately predicted MetS status, suggesting an additive mechanism in obesity-related metabolic disorders.

Melatonin exerts direct inhibitory actions on ACTH responses in the human adrenal gland.

In nonhuman primates and rodents, melatonin acting directly on the adrenal gland, inhibits glucocorticoid response to ACTH. In these species, an intrinsic adrenal circadian clock is involved in ACTH-stimulated glucocorticoid production. We investigated whether these findings apply to the human adrenal gland by determining i) expression of clock genes in vivo and ii) direct effects of melatonin in ACTH-stimulated adrenal explants over a) expression of the clock genes PER1 (Period 1) mRNA and BMAL1 [Brain-Muscle (ARNT)-like] protein, ACTH-induced steroidogenic acute regulatory protein (StAR), and 3ß-hydroxysteroid dehydrogenase (3ß-HSD) and b) over cortisol and progesterone production. Adrenal tissue was obtained from 6 renal cancer patients undergoing unilateral nephrectomy-adrenalectomy. Expression of the clock genes PER1, PER2, CRY2 (Cryptochrome 2), CLOCK (Circadian Locomotor Output Cycles Kaput) and BMAL1, was investigated by RT-PCR in a normal adrenal and in an adenoma. In independent experiments, explants from 4 normal adrenals were preincubated in culture medium (6 h) followed by 12 h in: medium alone; ACTH (100 nM); ACTH plus melatonin (100 nM); and melatonin alone. The explants' content of PER1 mRNA (real-time PCR) and StAR, 3ß-HSD, BMAL1 (immuno slot-blot), and their cortisol and progesterone production (RIA) were measured. The human adrenal gland expresses the clock genes PER1, PER2, CRY2, CLOCK, and BMAL1. ACTH increased PER1 mRNA, BMAL1, StAR, and 3ß-HSD protein levels, and cortisol and progesterone production. Melatonin inhibited these ACTH effects. Our study demonstrates, for the first time, direct inhibitory effects of melatonin upon several ACTH responses in the human adrenal gland.

Clock gene expression in adult primate suprachiasmatic nuclei and adrenal: is the adrenal a peripheral clock responsive to melatonin?

The circadian production of glucocorticoids involves the concerted action of several factors that eventually allow an adequate adaptation to the environment. Circadian rhythms are controlled by the circadian timing system that comprises peripheral oscillators and a central rhythm generator located in the suprachiasmatic nucleus (SCN) of the hypothalamus, driven by the self-regulatory interaction of a set of proteins encoded by genes named clock genes. Here we describe the phase relationship between the SCN and adrenal gland for the expression of selected core clock transcripts (Per-2, Bmal-1) in the adult capuchin monkey, a New World, diurnal nonhuman primate. In the SCN we found a higher expression of Bmal-1 during the h of darkness (2000-0200 h) and Per-2 during daytime h (1400 h). The adrenal gland expressed clock genes in oscillatory fashion, with higher values for Bmal-1 during the day (1400-2000 h), whereas Per-2 was higher at nighttime (about 0200 h), resulting in a 9- to 12-h antiphase pattern. In the adrenal gland, the oscillation of clock genes was accompanied by rhythmic expression of a functional output, the steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase. Furthermore, we show that adrenal explants maintained oscillatory expression of Per-2 and Bmal-1 for at least 36 h in culture. The acrophase of both transcripts, but not its overall expression along the incubation, was blunted by 100 nm melatonin. Altogether, these results demonstrate oscillation of clock genes in the SCN and adrenal gland of a diurnal primate and support an oscillation of clock genes in the adrenal gland that may be modulated by the neurohormone melatonin.

Maternal melatonin effects on clock gene expression in a nonhuman primate fetus.

In the adult mammal the circadian system, which allows predictive adaptation to daily environmental changes, comprises peripheral oscillators in most tissues, commanded by the suprachiasmatic nucleus (SCN) of the hypothalamus. The external environment of the fetus is provided by its mother. In primates, maternal melatonin is a candidate to entrain fetal circadian rhythms, including the SCN rhythms of metabolic activity. We found in the 90% of gestation capuchin monkey fetus expression of the clock genes Bmal-1, Per-2, Cry-2, and Clock in the SCN, adrenal, pituitary, brown fat, and pineal. Bmal-1, Per-2, and the melatonin 1 receptor (MT1) showed a robust oscillatory expression in SCN and adrenal gland, whereas a circadian rhythm of dehydroepiandrosterone sulphate was found in plasma. Maternal melatonin suppression changed the expression of Bmal-1, Per-2, and MT1 in the fetal SCN. These effects were reversed by maternal melatonin replacement. In contrast, neither maternal melatonin suppression nor its replacement had effects on the expression of Per-2 and Bmal-1 or MT1 in the fetal adrenal gland or the circadian rhythm of fetal plasma dehydroepiandrosterone sulphate. Our data suggest that maternal melatonin is a Zeitgeber for the fetal SCN but probably not for the adrenal gland.

New splicing mutation of MEN1 gene affecting the translocation of menin to the nucleus.

UNLABELLED: Multiple endocrine neoplasia type 1 (MEN1) is a syndrome inherited in an autosomal dominant trait caused by the inactivation of the tumor suppressor gene MEN1. OBJECTIVE: To communicate a family with a new heterozygous germ line mutation in the intronic region of MEN1 gene and to study its influence in the menin expression. PATIENTS AND METHODS: We studied 5 members of a family with symptomatic hyperparathyroidism (HPT). One of them had also a neuroendocrine pancreatic tumor, and 2 had non-functional multinodular cortical adrenal hyperplasia compatible with the diagnosis of MEN1. After the mutation was identified, HSP92II restriction enzyme was used to determine both zygosity and segregation of the mutation. RT-PCR from leukocyte's isolated mRNA and western blot from pancreatic tumor tissue were performed. In vitro studies were done in Chinese hamster ovary (CHO) cells transfected with reporter minigenes carrying the coding regions spanning exon (EX)-intron 9 and EX10 with the mutant and the wild type sequences. RESULTS: We identified a heterozygous G-to-T substitution in the intron-EX junction (IVS9-1 G>T) of MEN1 gene in the index case and the family members. The mRNA from patient's leukocytes was larger (934 bp) in comparison to the normal transcript (717 bp). Immunoblot analysis demonstrated that wild type (67 kDa) and two additional mutant proteins (approximately 55 and approximately 90 kDa) were expressed in the pancreatic tissue. The in vitro study showed a 45% nuclear localization of the mutated menin signal and a 95% in the wild type protein. CONCLUSIONS: We identified a new intronic heterozygous germ line mutation (IVS9-1G>T) of MEN1 gene in a family affected by MEN1 syndrome. This mutation alters the splice acceptor site of intron 9 that promotes an incorrect splicing, generating aberrant proteins without the nuclear localization signals necessary for the normal menin translocation to the nucleus.

Hyperprolactinemia and galactorrhea: spontaneous versus iatrogenic hypothyroidism.

Although hyperprolactinemia and galactorrhea occur in primary hypothyroidism, factors influencing their presence are not well established. To further define these factors, the duration of illness and serum levels of PRL and TSH were investigated in a group of 50 patients with spontaneous (27 females and 7 males) and iatrogenic (16 females) primary hypothyroidism. To test the hypothesis of reduced hypothalamic dopamine content in over long-standing primary hypothyroidism, the percent increase in serum PRL after the administration of metoclopramide, a dopamine blocker (2.5 mg, iv bolus), was studied in 13 women with spontaneous primary hypothyroidism and compared with that in 10 euthyroid women. While 88.2% of the patients with spontaneous primary hypothyroidism were hyperprolactinemia, only 31% of those with iatrogenic disease had elevated PRL levels. Women with spontaneous primary hypothyroidism had a longer duration of illness (72 +/- 12 vs. 6.7 +/- 1.8 months; P less than 0.001) and higher serum TSH (189 +/- 32 vs. 68 +/- 14 microunits/ml; P less than 0.01) and PRL levels (49.8 +/- 5.6 vs. 20.9 +/- 0.8 ng/ml; P less than 0.001) than women with iatrogenic hypothyroidism. A linear correlation existed between PRL and duration of illness (r = 0.53; P less than 0.001), while a logarithmic correlation was found between PRL and TSH levels (r = 0.44; P less than 0.01). Even though the duration of illness and TSH levels were similar in women with spontaneous disease with (n = 7) or without (n = 20) galactorrhea, the former were significantly younger (39.3 +/- 1.8 vs. 56.6 +/- 3 yr; P less than 0.001), and their PRL levels were significantly higher (69.3 +2- 8.9 vs. 42.9 +/- 2.2 ng/ml; P less than 0.001). The PRL response to metoclopramide in women with spontaneous disease was significantly smaller than that in controls (194 +/- 39% vs. 446 +/- 40%; P less than 0.001) and inversely correlated with basal PRL levels (r = -0.55; P less than 0.05). These data indicate that in primary hypothyroidism 1) the duration of illness is important in the development of hyperprolactinemia, 2) galactorrhea is more common in young women with spontaneous disease and high PRL levels, and 3) hypothalamic dopamine appears reduced in spontaneous disease.

Certain large forms of circulating immunoreactive human growth hormone are in fact immunoglobulins.

To explain frequent discordances between serum GH levels and clinical manifestation of acromegaly, we investigated the possibility that certain immunoglobulins G (IgGs) might be responsible for the displacement of [125I]human (h) GH in the hGH RIA. We incubated dilute sera from seven active acromegalics (basal immunoreactive hGH, 22-313 micrograms/L) with rat adipocyte plasma membranes adsorbed on polystyrene plates. IgGs that bound to GH receptor sites in the absence and presence of 250 nM hGH (for nonspecific binding) were detected using anti-hIgG (Fc-specific) antibody conjugated with alkaline phosphatase. In this system two of the seven sera studied tested positive for IgGs against GH-binding sites (serum 4 in 1:400 dilution, and serum 7 in 1:10 dilution). We studied further the serum with the highest titer. On Sephadex G-100, most of the GH-like immunoreactivity (assayed by RIA) present in serum 4 coeluted with IgGs (assayed by immunodiffusion) as a high mol wt (greater than or equal to 150 kDa) component. To confirm its IgG nature, this material was then adsorbed on protein-A-Sepharose and eluted with 0.1 M sodium citrate, pH 3.0. The protein-A-purified IgGs from serum 4 bound specifically to GH receptor sites in adipocyte membranes and displaced [125I]hGH in the hGH RIA. In contrast, IgGs purified from another acromegalic patient (313 micrograms/L hGH) repeatedly tested negative in the membrane binding assay and hGH RIA.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin bioactivity and the duration of lactational amenorrhea.

In our population, only half of fully nursing women remain amenorrheic 6 months postpartum. The other half recover their menstrual cycles between 90-180 days postpartum in spite of a high suckling frequency and elevated immunoreactive PRL (IR-PRL) concentrations. To further investigate the association of PRL with the recovery of ovarian function, we compared PRL bioactivity (BIO-PRL) 3-4 months postpartum in fully nursing amenorrheic women who subsequently experienced long (> 180 days; n = 5) or short (< 180 days; n = 5) lactational amenorrhea. In the present study, BIO-PRL in plasma was measured by the Nb2 lymphoma cell assay in samples taken before and 30 min after a suckling episode at 0800, 1600 and 2400 h. Women in the long amenorrhea group had higher overall mean BIO-PRL (mean +/- SE, 129.9 +/- 12.1 micrograms/L) than nursing women in the short amenorrhea group (66.6 +/- 5.2 micrograms/L; P < 0.05). Mean basal values were similar, but the women in the long amenorrhea group had more BIO-PRL in response to suckling (160.1 +/- 4.0 vs. 71.9 +/- 6.7 micrograms/L; P < 0.05). Compared with their respective basal values, nursing women in the long amenorrhea group demonstrated increased BIO-PRL in response to suckling, whereas the other group did not. The relationships between BIO-PRL and IR-PRL were similar in the two groups of nursing women before suckling. However, after suckling, the long amenorrhea group had significantly higher BIO-PRL levels than IR-PRL levels (P < 0.05, by likelihood test) than the short amenorrhea group. This suggests that suckling differentially changes in each group either the composition of PRL present or substances that may modify the bioactivity of PRL in plasma.

Growth hormone (GH) receptor antibodies with GH-like activity occur spontaneously in acromegaly.

Previous studies in our laboratory have identified a portion of big-big GH as actually being anti-GH receptor immunoglobulins. We now report the isolation of two types of anti-GH receptor antibodies from the serum of active acromegalic patients. One of them (patient A) interferes with the human GH RIA, thus overestimating the real plasma GH values. The other type of immunoglobulin G (IgG; patient B) was detected in an acromegalic patient with almost normal immunoreactive GH level. The main aim of the present study was to explore whether these anti-GH receptor IgGs possess GH-like biological activity. The IgGs of both patients were isolated by chromatography on Sephadex G-100 and then on protein-A-Sepharose. In the bioassay, cultured Nb2 lymphoma cells were incubated with hGH standards and serial dilutions of the purified IgGs, and cell proliferation was used as a measure of biological activity. The IgGs of both patients showed GH-like bioactivities, which, when calculated as equivalents of human GH, correspond to approximately 260 and 120 micrograms/L, respectively. The results suggest that biologically active anti-GH receptor antibodies may contribute in the pathology of some cases of acromegaly.

Serum osteocalcin in normal menstrual cycle.

Serum osteocalcin (OC) was serially measured along an ovulatory menstrual cycle in 4 healthy unmedicated volunteers (age 33-38 years). During the study the women maintained their normal diet and daily physical activity. Starting at days 4-5 of the cycle, blood samples were taken between 09-11 AM every 2 or 3 days for OC, FSH, LH, E2 and P determinations. Daily ultrasound assessment of ovulation was performed in all subjects between days 7-18 of the cycle. Hormone determinations and OC were performed by RIA. While blood levels of FSH, LH, E2 and P changed during the cycle, according to the expected ovulatory pattern, serum OC concentrations remained stable during the cycle in each subject. In conclusion, serum OC is independent of the gonadotropin and ovarian steroid variations during the normal menstrual cycle.

Immune system alterations by aldosterone during hypertension: from clinical observations to genomic and non-genomic mechanisms leading to vascular damage.

Hypertension is traditionally considered a disease in which elevated blood pressure contributes to inflammation and activation of the immune system, leading to cardiovascular injury and end-organ damage. Here, we discuss the effects of aldosterone on the immune system and aldosterone's contribution to vascular pathogenesis. Studies in human have suggested a broader role for aldosterone, beyond elevating blood pressure. Recent clinical data support the notion that aldosterone can directly alter the function of the immune system and cause vascular-damaging inflammation. Clinical observations have been reproduced in experimental models of hypertension, further supporting the idea that an aberrant immune response contributes to the onset of hypertension. Such studies have shown that myeloid cells are required to induce the disease and IL-17-producing CD4(+) T cells may contribute to maintaining aldosterone-mediated hypertension. In addition, regulatory T cells diminish the inflammatory damage caused by aldosterone during hypertension. This is a very active area of research that could lead to new therapeutic targets for treating hypertension.

[Plasma calcium levels in critical patients with and without sepsis]. / Niveles de calcio plasmático en pacientes críticos con y sin sepsis.

We determined total plasma calcium levels in 44 critically ill patients without evidence of renal or hepatic failure, 25 of them with active systemic infection. Plasma Ca was 7.49 +/- 0.1 mg/dl in the septic group compared to 8.46 +/- 0.2 in non septic patients (p < 0.01). Corresponding levels of serum albumin were 2.26 +/- 0.1 and 3.05 +/- 0.2 milligrams, respectively (p < 0.01). Corresponding corrected plasma Ca levels were 9.19 +/- 0.1 and 9.39 +/- 0.1 mg/dl (NS). No correlation of lactate and plasma Ca levels was found. Mortality was 56% for septic and 16% for non septic patients. Patients with hypocalcemia had 53% mortality rate compared to only 16% in normocalcemic patients. PTH levels were normal in all but one patients, thus ruling out a rapid installation secondary hyperparathyroidism. Hypoperfusion does not appear related to ionic Ca levels given the lack of correlation of Ca and lactate levels. Mortality is related to sepsis and hypoalbuminemia but not to corrected Ca plasma levels.

[Active acromegaly and gigantism: some clinical characteristics of 50 patients]. / Acromegalia y gigantismo activos:algunas características clínicas de 50 pacientes.

50 patients with autonomous growth hormone excess (48 with adult acromegaly and 2 with gigantism) were studied between 1966 to 1986 (2.38 pts/year). Characteristic clinical presentation, an increase in growth hormone (GH) uninhibited by glucose, and/or hyperphosphemia and hyperhydroxiprolinuria were present in all patients. No cases of hypercalcemia were recorded. Phosphemia was increased in 55.8%, alkaline phosphatases in 61.7%, calciuria in 26.9% and hydroxyprolinuria in 74.2% of the patients. Basal GH was over 5 ng/ml (89.9 DS +/- 170.9) in 42 pts, and in 37 was not suppressed after glucose administration, 38% had an increased (paradoxical response) and 62% a flat response (less than 50% change of basal values). TRH test was performed in 14 patients, 8 presented an increase in GH titer. Hyperprolactinemia was seen in 4 of 12 patients in whom this hormone was measured. The size of the sella turcica was increased in 93%, and although the larger sellar size correlated to higher levels of GH, correlation was not significant. 20% of the pts had rheumatological disease, 14% goiter, 12% cardiac disease, 26.5% had diastolic hypertension and 4% renal lithiasis (hypercalciuric pts). 38% had hyperglycemia with a diabetic glucose tolerance test and 18% had non-diabetic abnormal glucose tolerance test.

[Hyperthyroxinemia and clinical euthyroidism. Report of one case]. / Hipertiroxinemia con eutiroidismo clínico: análisis a propósito de un caso.

The association of hyperthyroxinemia and euthyroidism is frequent and characterized by high plasma thyroxin concentrations, normal TSH values and absence of clinical signs of hyperthyroidism. We report an asymptomatic 28 years old male presenting with a serum total plasma thyroxin of 18.5 micrograms/dl (N 6.1-12.5), a free thyroxin of 2.9 ng/dl (N 0.8-1.4), a TSH of 3.4 microIU/ml (N 0.5-5), and a triiodothyronine of 128 ng/dl (N 80-180). Laboratory assessment did not find high thyroxin binding globulin, albumin or prealbumin concentrations or antithyroxin antibodies. The thyroxin binding capacity of albumin was elevated to 58.2 micrograms/dl (N 11.5-34.1). TSH responded normally to TRH stimulus and was suppressed with exogenous triiodothyronine, which caused an hyperthyroid syndrome. We concluded that this patient had a familial dysalbuminemia.

[Idiopathic hypoparathyroidism, a syndrome with various clinical expressions: analysis of 10 cases]. / Hipoparatiroidismo idiopatico, un sindrome con variadas expresiones clinicas: analisis de 10 casos.

We report 10 patients with primary hypoparathyroidism. Age at onset varied from 7 months to 52 years (mean 28); 7 were female. Diagnosis was established at a mean of 4.1 years after the appearance of clinical manifestations. Unexplained hypocalcemia (mean 5.3 mg/dl) and hyperphosphatemia (mean 6.4 mg/dl) were present in all patients. Prevalent symptoms included tetany (9 patients), seizures (5) and hypocalcemic cataracts (4). Clinical manifestations may be grouped into 5 types 1) tetany; 2) seizures; 3) other neurologic disorders (basal ganglia calcification, pseudotumor of the brain, ataxia, nystagmus, hypertonus, paresis); 4) disorders of the lens including fully developed cataracts and 5) skin alterations like psoriasis and others. Some of these run on acute course (seizures, tetany), others a subacute one (skin alterations) while others are rather chronic (cataract and other neurologic disorders). Seizures and electroencephalographic disorders predominate in younger patients while tetany is more prevalent in older subjects.

Post-suckling prolactin:oestradiol ratio--a potential index to predict the duration of lactational amenorrhoea in women.

To assess whether the duration of lactational amenorrhoea can be predicted in individual women, we studied the pre- and post-suckling concentrations of immune prolactin (IR-PRL) and of bioactive prolactin (BIO-PRL) and basal concentrations of oestradiol in ten amenorrhoeic fully nursing women at 3 months post-partum. The women were of similar age, weight and had infants of similar growth rate. Five of these women were to experience long amenorrhoea (>180 days) and the others short amenorrhoea (<180 days). Blood samples were drawn 30 min after a suckling episode initiated at 0800 h, 1600 h and 2400 h. BIO-PRL distinguished between groups of women at 0030 h but not at other times, while there was considerable overlap between values for IR-PRL and oestradiol at all times studied. At 1630 h, the ratios post-suckling BIO-PRL: oestradiol and post-suckling IR-PRL:oestradiol were above 2000 in the women that were to experience long amenorrhoea and below this threshold in the other women. The ratio post-suckling BIO-PRL:oestradiol provided more information since the difference between the lowest ratio in the long amenorrhoea and the highest ratio in the short was 699, while it was 520 for the IR-PRL:oestradiol ratio. The determination of these ratios may help to predict the duration of lactational amenorrhoea in individual fully nursing women.

Bone turnover and density in healthy women during breastfeeding and after weaning.

To investigate the changes in maternal bone density and turnover associated with lactation we ran a longitudinal study in fully breastfeeding women (age 26.3 +/- 4.1 years, mean +/- SD) at the first (stage I, n = 30) and sixth (stage II, n = 25) months postpartum and 6 months after weaning (stage III, n = 20), and in a contemporary control group of non-nursing women. At each time point bone density, serum calcium, phosphorus, alkaline phosphatases, parathyroid hormone (PTH), osteocalcin, follicle stimulating hormone (FSH), estradiol (E2), prolactin (PRL) urinary hydroxyproline and creatinine (OH-P/Cr) were measured in both groups. The daily calcium intake of nursing women (1479 +/- 590 mg/day at stage I) was higher than in non-nursing women (536 +/- 231 mg/day at stage I). Biochemical markers of bone turnover were higher (p < 0.05) in nursing than in non-nursing women at stages I and II, while in stage III only OH-P/Cr was elevated. The lumbar spine (L2-4) bone mineral density was similar in the two groups at the beginning of the study (1.148 +/- 0.111 g/cm2 in nursing women vs 1.211 +/- 0.102 g/cm2 in non-nursing women; p = 0.06), but it was lower in nursing women at stage II (1.144 +/- 0.110 g/cm2 vs 1.216 +/- 0.095 g/cm2 respectively; p < 0.05). Right femoral neck bone density decreased by 3% between stages I and II in nursing women but did not differ from values in non-nursing women (0.947 +/- 0.110 vs 0.973 +/- 0.108 in stage I and 0.918 +/- 0.114 vs 0.975 +/- 0.098 in stage II respectively; p < 0.05, ANOVA). After weaning, lumbar spine and femoral neck bone density increased by 6% and 8% respectively (p < 0.05, ANOVA). No correlation was found between changes in bone turnover markers or bone density and parity, frequency and duration of nursing episodes, body weight, body mass index, and plasma PRL, E2 and PTH levels. We conclude that in nursing women with a daily calcium intake at the recommended dietary allowance ( > 1200 mg/day), full breastfeeding extending over 6 months is characterized by increased maternal bone turnover and a transient bone loss which normalizes after weaning.

Bioactivity of prolactin isoforms: lactation and recovery of menses in nursing women.

To assess whether plasma prolactin (PRL) characteristics relate to lactogenesis and absence or presence of menstrual cycles, we measured bioactive PRL (BIO-PRL) using the Nb2 assay, immunoreactive PRL (IR-PRL) by radio-immunoassay, calculated equations describing the BIO-PRL-IR-PRL relationship and separated charged PRL isoforms (by chromatofocusing) in five amenorrhoeic and five cycling nursing women at 6 months postpartum and in 10 cycling non-nursing women. Plasma samples were drawn before and 30 min after a suckling episode at 0800, 1600 and 2400 h in nursing women and at the same hours in non-nursing women. BIO-PRL and IR-PRL concentrations were highest in amenorrhoeic nursing women, intermediate in cycling nursing women and lowest in cycling non-nursing women. The BIO-PRL-IR-PRL relationship shows that a given amount of IR-PRL corresponds to equivalent amounts of BIO-PRL in cycling nursing and cycling non-nursing women, and to a larger extent in amenorrhoeic nursing women. IR-PRL was present in plasma as several charge isoforms. Bioactive isoforms eluting at pH 6.0-5.1 were found in amenorrhoeic and cycling nursing women, reaching similar concentrations after suckling. Bioactive isoforms eluting at pH 7.0-6.1 were found only in amenorrhoeic nursing women. We speculate that isoforms eluting at pH 6.0-5.1 may play a role in lactation and isoforms eluting at pH 7.0-6.1, in lactational amenorrhoea.