Egil Haug

Low Serum Calcidiol Concentration in Older Adults with Reduced Muscular Function

OBJECTIVE: To examine the association between muscular function and the serum concentrations of 25‐hydroxyvitamin D (calcidiol) and 1,25‐dihydroxyvitamin D (calcitriol).

Prevalence and predictors of vitamin D deficiency in five immigrant groups living in Oslo, Norway: the Oslo Immigrant Health Study

Objective: To study the prevalence of vitamin D deficiency and to identify possible predictors of vitamin D deficiency in five main immigrant groups in Oslo.Design: Cross-sectional, population-based.Setting: City of Oslo.Subjects: In total, 491 men and 509 women with native countries Turkey, Sri Lanka, Iran, Pakistan and Vietnam living in the county of Oslo.Results: Median serum 25(OH)D level (s-25(OH)D) was 28 nmol/l, ranging from 21 nmol/l in women born in Pakistan to 40 nmol/l in men born in Vietnam. Overall prevalence of vitamin D deficiency defined as s-25(OH)D<25 nmol/l was 37.2%, ranging from 8.5% in men born in Vietnam to 64.9% in women born in Pakistan. s-25(OH)D did not vary significantly with age. s-25(OH)D was higher in blood samples drawn in June compared to samples obtained in April, but not significantly for women. Reported use of fatty fish and cod liver oil supplements showed a strong positive association with s-25(OH)D in all groups. Education length was positively associated with s-25(OH)D in women, whereas body mass index (BMI) was inversely associated with s-25(OH)D in women. These two variables were not related to vitamin D deficiency in men.Conclusions: There is widespread vitamin D deficiency in both men and women born in Turkey, Sri Lanka, Iran, Pakistan and Vietnam residing in Oslo. The prevalence of vitamin D deficiency is higher in women than in men, and it is higher in those born in Pakistan and lower in those born in Vietnam compared to the other ethnic groups. Fatty fish intake and cod liver oil supplements are important determinant factors of vitamin D status in the groups studied. BMI and education length are also important predictors in women.Sponsorship: Supported by the Directorate for Health and Social Affairs, Oslo, and Research Forum, Aker University Hospital, Oslo.

hCG suppression of LH receptors and responsiveness of testicular tissue to hCG

A single injection of 75 IU of human chorionic gonadotropin (hCG) into adult male rats caused a dramatic reduction in the concentration of membrane receptors for luteinizing hormone (LH) in the testis. The mean receptor level reached a nadir which was 5--10% of that in the control testes, 3 days after the injection, after which it gradually returned toward normal. This cannot be due to increased competition caused by the injected hCG since no decrease was observed at a time when the circulating levels of hCG were at a maximum (2--24 h after injection). Furthermore, at a time when receptor levels had been maximally reduced, circulating hCG was at or below the level of detection. Reduction in the number of LH binding sites in the testis was associated with a decreased responsiveness of the testicular tissue to hCG as measured by hCG-stimulated testosterone production in vitro. This inhibitory effect of large quantities of LH on its own receptor is suggested as a possible explantation for the previously observed low concentrations of LH receptor in the testis of the testicular feminized male (tfm) rat. This syndrome is characterized by high endogenous levels of plasma LH (Sherins et al., 1971).

Vasoactive intestinal peptide and peptide with N-terminal histidine and C-terminal isoleucine increase prolactin secretion in cultured rat pituitary cells (GE4C1) via a cAMP-dependent mechanism which involves transient elevation of intracellular Ca2+

Vasoactive intestinal peptide (VIP) and peptide (P) with N-terminal histidine and C-terminal isoleucine (PHI) stimulated prolactin (PRL) secretion from GH4C1 cells equipotent with ED50 values of 30-50 nM. In a parafusion system optimized to give high time resolution both VIP and PHI increased PRL secretion with a delay of about 60 s and subsequent to the activation of the adenylate cyclase. Thyroliberin (TRH) increased PRL secretion within 4 s. The dose-response curves for VIP- and PHI-stimulated cAMP accumulation were superimposable on those for PRL secretion. At submaximal concentrations the effects of VIP and PHI on both cAMP accumulation and PRL secretion were additive, whereas the effects were not additive at concentrations giving maximal effects. VIP and PHI increased [Ca2+]i measured by quin-2 in a different way than TRH, without inducing changes in the electrophysiological membrane properties of the GH4C1 cells. We conclude that both VIP and PHI stimulate PRL secretion via a cAMP-dependent process involving an increase in [Ca2+]i.

Stimulation with human menopausal gonadotropin versus follicle-stimulating hormone after pituitary suppression in polycystic ovarian syndrome

Stimulation with human menopausal gonadotropin (hMG) or follicle-stimulating hormone (FSH) was compared in 34 patients with polycystic ovarian syndrome after pituitary gonadotrope suppression with buserelin acetate. No differences were seen in the hormone parameters observed. Also, the duration of the stimulation period and the dose of gonadotropin used were the same. In both groups a multifollicular response was seen. Oocyte retrieval and in vitro fertilization resulted in identical ratios of mature to total oocytes and cleavage rates. Nine pregnancies occurred, four in the hMG group and five in the FSH group. Of the nine pregnancies, two were the result of transfer of frozen-thawed embryos in estradiol and progesterone substituted cycles.

Plasma oestrogens in postmenopausal women with endometrial cancer

Objective To study plasma levels of oestrogens and androgens, sex hormone‐binding globulin (SHBG) and follicle stimulating hormone (FSH) in postmenopausal patients with endometrial cancer.

Cross-sex pattern of bone mineral density in early onset gender identity disorder

Hormonally controlled differences in bone mineral density (BMD) between males and females are well studied. The effects of cross-sex hormones on bone metabolism in patients with early onset gender identity disorder (EO-GID), however, are unclear. We examined BMD, total body fat (TBF) and total lean body mass (TLBM) in patients prior to initiation of sex hormone treatment and during treatment at months 3 and 12. The study included 33 EO-GID patients who were approved for sex reassignment and a control group of 122 healthy Norwegians (males, n=77; females, n=45). Male patients (n=12) received an oral dose of 50 mug ethinylestradiol daily for the first 3 months and 100 mug daily thereafter. Female patients (n=21) received 250 mg testosterone enantate intramuscularly every third week. BMD, TBF and TLBM were estimated using dual energy X-ray absorptiometry (DXA). In male patients, the DXA measurements except TBF were significantly lower compared to their same-sex control group at baseline and did not change during treatment. In female patients, the DXA measurements were slightly higher than in same-sex controls at baseline and also remained unchanged during treatment. In conclusion, this study reports that body composition and bone density of EO-GID patients show less pronounced sex differences compared to controls and that bone density was unaffected by cross-sex hormone treatment.

Receptors for 17β-estradiol in prolactin-secreting rat pituitary cells

Abstract Estrogens stimulate prolactin (PRL) synthesis by GH3 cells, a clonal strain of rat pituitary cells grown in culture. At 4°C the binding of [3H] 17β-estradiol to monolayer cultures of GH3 cells was specific and of limited capacity, with half-maximal and maximal binding after 1–2 h and 12 h, respectively. Scatchard analysis showed one single class of binding sites with Kd = 3.1 × 10−10 M and n = 309 × 10−15 mol 17β-estradiol/mg cell protein, calculated to give approx. 25,000 binding sites per cell. At 4°C We suggest that the action of 17β-estradiol on GH3 cells involves an initial binding of the steroid to specific receptors in the cytoplasm, followed by transport of a fraction of the hormone—receptor complexes to the nucleus involving a temperature-sensitive step.

Validation of a radioreceptor assay for 1,25-dihydroxyvitamin D using selected ion monitoring GC-MS.

This report describes two methods for the measurement of 1,25-dihydroxyvitamin D [1,25(OH)2D] in serum: A modified radio receptor assay (RRA), employing a 1,25(OH)2D receptor from calf thymus, and selected ion monitoring (SIM) with combined capillary gas chromatography (GC)-mass spectrometry (MS). The intra-assay coefficient of variation was close to 13% for both methods, and the inter-assay coefficients of variation were 14.0 and 6.5% for RRA and SIM (GC-MS), respectively. Aliquots of 2 ml (RRA) and 20 ml (SIM) serum were used, and the limits of detection were 10 and 6 pmol/l, respectively. The analytical recovery of each method was assessed, and a maximum deviation from the expected value of 10 and 2% was found for RRA and SIM, respectively. A correlation coefficient of 0.93 (slope 0.97) was obtained when 27 different serum samples were analyzed by both methods. Included in this study were serum samples from healthy subjects and patients with subnormal as well as supranormal 1,25(OH)2D levels. This result showed that the RRA accurately measured the serum levels of 1,25(OH)2D and therefore should be useful in the diagnosis and control of vitamin D dependent diseases.

The Mechanisms by Which Vasoactive Intestinal Peptide (VIP) and Thyrotropin Releasing Hormone (TRH) Stimulate Prolactin Release from Pituitary Cells

The effect of vasoactive intestinal peptide (VIP) on prolactin (PRL) secretion from pituitary cells is reviewed and compared to the effect of thyrotropin releasing hormone (TRH). These two peptides induced different secretion profiles from parafused lactotrophs in culture. TRH was found to increase PRL secretion within 4 s and induced a biphasic secretion pattern, while VIP induced a monophasic secretion pattern after a lag time of 45–60 s.The secretion profiles are compared to changes in adenylate cyclase activity, production of inositol polyphosphates, changes in intracellular calcium concentrations and changes in electrophysiological properties of the cell membrane.