Hormone replacement therapy increases serum 1,25-dihydroxyvitamin D: A 2-year prospective study

Vitamin D deficiency associated with reproductive factors in northern Iranian women: The PERSIAN Guilan Cohort Study (PGCS)

BACKGROUND

One of the public health concerns is Vitamin D deficiency. The aim of this study was to determine the prevalence of vitamin D inadequacy and to determine its reproductive factor correlates in northern Iranian women.

METHODS

This study, conducted on 5096 females aged 35-70 years. The study was based on data from PERSIAN Guilan Cohort Study (PGCS), a prospective, population-based cohort study in Guilan, Iran. History of reproductive and gynecologic factors, including age at menarche, age at first marriage, number of pregnancies or live births, age at first pregnancy, duration of breastfeeding, number of abortions, age and type of menopause status, use of oral contraceptives or hormone replacement therapy, history of hysterectomy, tubectomy or oophorectomy and history of gestational diabetes and hypertension was collected. Serum 25(OH) vitamin D was measured.

RESULTS

The mean 25(OH)-D concentration was 21.78 ng/mL, and 53.5% of women had vitamin D inadequacy. The multivariate analyses revealed that younger age (36-45 years) [>66 years adjusted odds ratio (aOR) = 2.1, 95% CI 1.7-2.7, 56-65 years aOR = 1.7, 95% CI 1.3-2.1 and 46-55 years aOR = 1.4, 95% CI 1.1-1.7], not consuming oral contraceptives [aOR = 1.1, 95% CI 1.05-1.3] and pre-menopausal status [aOR = 1.4, 95% CI 1.2-1.6] were significantly independently associated with vitamin D inadequacy.

CONCLUSION

Vitamin D inadequacy is common in northern Iranian women. The reproductive factors that independently correlated with vitamin D statues are oral contraceptive consumption and menopausal statue.

Vitamin D status among adults in Germany--results from the German Health Interview and Examination Survey for Adults (DEGS1)

Background

In 1998, more than half of the adult population in Germany had serum 25-hydroxy-vitamin-D [25(OH)D] levels below the common threshold of 50 nmol/l. Since then, there has been a lot of attention for vitamin D in the scientific community, the media and the general population and serum 25(OH)D levels may have increased as a consequence. With data from the ‘German Health Interview and Examination Survey for Adults’ (DEGS1) the current situation of vitamin D status can be analysed.

Methods

DEGS1, a national health survey among adults in Germany conducted by the Robert Koch Institute between 2008 and 2011, included 6,995 persons with available serum 25(OH)D levels. We calculated the proportion of participants with serum 25(OH)D levels <30 nmol/l, 30- < 50 nmol/l and > =50 nmol/l overall and according to age, season and latitude of residence as well as percentiles of serum 25(OH)D according to month of examination. Determinants of vitamin D status were analysed with multiple linear regression models.

Results

Mean serum 25(OH)D level was 45.6 nmol/l with no significant sex differences (p = 0.47). 61.6 % of the participants had serum 25(OH)D levels <50 nmol/l, 30.2 % had levels <30 nmol/l. During summer, half of the participants had levels > =50 nmol/l, during winter time, 25 % of the participants had levels <30 nmol/l. A significant latitudinal gradient was observed in autumn for men and in winter for women.

In multiple linear regression analyses, examination during winter time, residing in northern latitude, non-use of vitamin D supplements, low sport activity, high Body Mass Index (BMI) and high media consumption were independently and significantly associated with lower serum 25(OH)D levels in both sexes. In addition, among women, significant associations with lower 25(OH)D levels were observed for older age and lower socio-economic status, among men, for low vitamin D intake and more residential traffic.

Conclusions

Serum 25(OH)D levels below the threshold of 50 nmol/l are still common among adults in Germany, especially during winter and spring and in higher latitudes. Potentially modifiable factors of poorer vitamin D status are higher BMI, lack of sport activity and high media use.

Vitamin D status among Thai school children and the association with 1,25-Dihydroxyvitamin D and parathyroid hormone levels

In several low latitude countries, vitamin D deficiency is emerging as a public health issue. Adequate vitamin D is essential for bone health in rapidly growing children. In the Thai population, little is known about serum 25-hydroxyvitamin D [25(OH)D] status of infants and children. Moreover, the association between 25(OH)D and the biological active form of 1,25-dihydroxyvitamin D [1,25(OH)]₂D is not clear. The specific aims of this study were to characterize circulating serum 25(OH)D, 1,25(OH)₂D and their determinants including parathyroid hormone (PTH), age, sex, height and body mass index (BMI) in 529 school-aged Thai children aged 6–14 y. Adjusted linear regression analysis was performed to examine the impact of age and BMI, and its interaction with sex, on serum 25(OH)D concentrations and 1,25(OH)₂D concentrations. Serum 25(OH)D, 1,25(OH)₂D and PTH concentrations (geometric mean ± geometric SD) were 72.7±1.2 nmol/L, 199.1±1.3 pmol/L and 35.0±1.5 ng/L, respectively. Only 4% (21 of 529) participants had a serum 25(OH)D level below 50 nmol/L. There was statistically significant evidence for an interaction between sex and age with regard to 25(OH)D concentrations. Specifically, 25(OH)D concentrations were 19% higher in males. Moreover, females experienced a statistically significant 4% decline in serum 25(OH)D levels for each increasing year of age (P = 0.001); no decline was seen in male participants with increasing age (P = 0.93). When BMI, age, sex, height and serum 25(OH)D were individually regressed on 1,25(OH)₂D, height and sex were associated with 1,25(OH)₂D with females exhibiting statistically significantly higher serum 1,25(OH)₂D levels compared with males (P<0.001). Serum 1,25(OH)₂D among our sample of children exhibiting fairly sufficient vitamin D status were higher than previous reports suggesting an adaptive mechanism to maximize calcium absorption.

Circulating 25-hydroxyvitamin D and postmenopausal breast cancer survival: Influence of tumor characteristics and lifestyle factors?

We previously reported that lower post-diagnostic circulating 25-hydroxyvitamin D [25(OH)D] concentrations were associated with higher risk of overall mortality and distant disease in stage I-IV postmenopausal breast cancer survivors. This association was now re-examined in an extended dataset to investigate potential effect modification by tumor characteristics and lifestyle factors. A prospective cohort study was conducted in Germany including 2,177 incident stage I-IV postmenopausal breast cancer patients aged 50-74 years. Patients were diagnosed between 2001 and 2005 and median follow-up time was 5.3 years. Cox proportional hazards models were stratified by age at diagnosis, study center and season of blood collection and adjusted for other prognostic factors. A meta-analysis of studies on circulating 25(OH)D and mortality in breast cancer patients was performed to summarize evidence. Lower concentrations of 25(OH)D were significantly associated with higher risk of overall mortality [hazard ratio (HR) lowest vs. highest tertile = 1.86; 95% confidence interval (CI): 1.22, 2.82; p-trend = 0.002] and distant disease (HR = 1.76; 95% CI: 1.24, 2.49; p-trend = 0.003) in stage I-IIIa but not in stage IIIb-IV breast cancer patients. No significant interaction by lifestyle factors was observed (all p-interaction > 0.05). The meta-analysis yielded significant associations with overall and breast cancer-specific mortality (lowest vs. highest quantile: HR = 1.52; 95% CI: 1.22, 1.88 and HR = 1.74; 95% CI: 1.23, 2.40, respectively). In conclusion, post-diagnostic circulating 25(OH)D concentrations were associated with overall mortality and distant disease in stage I-IIIa postmenopausal breast cancer patients. This association was not strongly modified by lifestyle factors.

Determinants of serum levels of vitamin D: a study of life-style, menopausal status, dietary intake, serum calcium, and PTH

Background

Low blood levels of vitamin D (25-hydroxy D3, 25OHD3) in women have been associated with an increased risk of several diseases. A large part of the population may have suboptimal 25OHD3 levels but high-risk groups are not well known. The aim of the present study was to identify determinants for serum levels of 25OHD3 in women, i.e. factors such as lifestyle, menopausal status, diet and selected biochemical variables.

Methods

The study was based on women from the Malmö Diet and Cancer Study (MDCS), a prospective, population-based cohort study in Malmö, Sweden. In a previous case–control study on breast cancer, 25OHD3 concentrations had been measured in 727 women. In these, quartiles of serum 25OHD3 were compared with regard to age at baseline, BMI (Body Max Index), menopausal status, use of oral contraceptives or menopausal hormone therapy (MHT) , life-style (e.g. smoking and alcohol consumption), socio-demographic factors, season, biochemical variables (i.e. calcium, PTH, albumin, creatinine, and phosphate), and dietary intake of vitamin D and calcium. In order to test differences in mean vitamin D concentrations between different categories of the studied factors, an ANOVA test was used followed by a t-test. The relation between different factors and 25OHD3 was further investigated using multiple linear regression analysis and a logistic regression analysis.

Results

We found a positive association between serum levels of 25OHD3 and age, oral contraceptive use, moderate alcohol consumption, blood collection during summer/ autumn, creatinine, phosphate, calcium, and a high intake of vitamin D. Low vitamin D levels were associated with obesity, being born outside Sweden and high PTH levels.

Conclusions

The present population-based study found a positive association between serum levels of 25OHD3 and to several socio-demographic, life-style and biochemical factors. The study may have implications e. g. for dietary recommendations. However, the analysis is a cross-sectional and it is difficult to suggest Lifestyle changes as cause- effect relationships are difficult to assess.

Plasma 1,25-dihydroxyvitamin D levels in primary hyperparathyroidism depend on sex, body mass index, plasma phosphate and renal function

BACKGROUND

Primary hyperparathyroidism (PHPT) is characterized by elevated plasma levels of PTH and calcium with reduced plasma phosphate. Physiologically, renal 1alpha,25-dihydroxyvitamin D [1,25(OH)(2)D] production is stimulated by PTH and phosphate deprivation, and inhibited by 1,25(OH)(2)D itself and calcium.

AIM

To investigate relations between circulating levels of 1,25(OH)(2)D, 25-dihydroxyvitamin D (25OHD), PTH, calcium, phosphate, renal function and skeletal complications in patients with PHPT.

DESIGN

Cross-sectional study.

MATERIAL

Two hundred and fifty-two consecutive hypercalcaemic Caucasian patients aged 24-91 (median 65.9) years (85.3% females) with PHPT.

RESULTS

In patients with PHPT, plasma 1,25(OH)(2)D was increased by 27%[107 (9-250) pmol/l, median (range)] compared to controls [84 (18-172) pmol/l, P < 0.001]. In univariate models, plasma 1,25(OH)(2)D depended inversely on age (r = -0.23, P < 0.001) and plasma phosphate (r = -0.23, P < 0.001) and positively on plasma calcium (r = 0.14, P < 0.05), plasma 25OHD (r = 0,15, P < 0.05) and creatinine clearance rate (r = 0.32, P < 0.001). In the final multiple regression model, plasma 1,25(OH)(2)D depended positively on renal function (r(p) = 0.43, P < 0.001) and female sex (r(p) = 0.15, P < 0.05) but inversely on body mass index (BMI; r(p) = -0.23, P < 0.005) and plasma phosphate (r(p) = -0.18, P < 0.05). Plasma 1,25(OH)(2)D correlated positively with renal calcium excretion and inversely with lumbar spine bone mineral density (BMD) but was not associated with risk of fractures or renal stones.

CONCLUSION

Patients with PHPT have elevated plasma 1,25(OH)(2)D levels but, to a large extent, individual values overlap controls. The increase in plasma 1,25(OH)(2)D depends on renal function, hypophosphataemia and the female sex and is attenuated by high BMI. High plasma 1,25(OH)(2)D is associated with higher plasma calcium levels.

Physical activity in the prevention and amelioration of osteoporosis in women : interaction of mechanical, hormonal and dietary factors

Osteoporosis is a serious health problem that diminishes quality of life and levies a financial burden on those who fear and experience bone fractures. Physical activity as a way to prevent osteoporosis is based on evidence that it can regulate bone maintenance and stimulate bone formation including the accumulation of mineral, in addition to strengthening muscles, improving balance, and thus reducing the overall risk of falls and fractures. Currently, our understanding of how to use exercise effectively in the prevention of osteoporosis is incomplete. It is uncertain whether exercise will help accumulate more overall peak bone mass during childhood, adolescence and young adulthood. Also, the consistent effectiveness of exercise to increase bone mass, or at least arrest the loss of bone mass after menopause, is also in question. Within this framework, section 1 introduces mechanical characteristics of bones to assist the reader in understanding their responses to physical activity. Section 2 reviews hormonal, nutritional and mechanical factors necessary for the growth of bones in length, width and mineral content that produce peak bone mass in the course of childhood and adolescence using a large sample of healthy Caucasian girls and female adolescents for reference. Effectiveness of exercise is evaluated throughout using absolute changes in bone with the underlying assumption that useful exercise should produce changes that approximate or exceed the absolute magnitude of bone parameters in a healthy reference population. Physical activity increases growth in width and mineral content of bones in girls and adolescent females, particularly when it is initiated before puberty, carried out in volumes and at intensities seen in athletes, and accompanied by adequate caloric and calcium intakes. Similar increases are seen in young women following the termination of statural growth in response to athletic training, but not to more limited levels of physical activity characteristic of longitudinal training studies. After 9-12 months of regular exercise, young adult women often show very small benefits to bone health, possibly because of large subject attrition rates, inadequate exercise intensity, duration or frequency, or because at this stage of life accumulation of bone mass may be at its natural peak. The important influence of hormones as well as dietary and specific nutrient abundance on bone growth and health are emphasised, and premature bone loss associated with dietary restriction and estradiol withdrawal in exercise-induced amenorrhoea is described. In section 3, the same assessment is applied to the effects of physical activity in postmenopausal women. Studies of postmenopausal women are presented from the perspective of limitations of the capacity of the skeleton to adapt to mechanical stress of exercise due to altered hormonal status and inadequate intake of specific nutrients. After menopause, effectiveness of exercise to increase bone mineral depends heavily on adequate availability of dietary calcium. Relatively infrequent evidence that physical activity prevents bone loss or increases bone mineral after menopause may be a consequence of inadequate calcium availability or low intensity of exercise in training studies. Several studies with postmenopausal women show modest increases in bone mineral toward the norm seen in a healthy population in response to high-intensity training. Physical activities continue to stimulate increases in bone diameter throughout the lifespan. These exercise-stimulated increases in bone diameter diminish the risk of fractures by mechanically counteracting the thinning of bones and increases in bone porosity. Seven principles of bone adaptation to mechanical stress are reviewed in section 4 to suggest how exercise by human subjects could be made more effective. They posit that exercise should: (i) be dynamic, not static; (ii) exceed a threshold intensity; (iii) exceed a threshold strain frequency; (iv) be relatively brief but intermittent; (v) impose an unusual loading pattern on the bones; (vi) be supported by unlimited nutrient energy; and (vii) include adequate calcium and cholecalciferol (vitamin D3) availability.

Vitamin D3Confers Protection from Autoimmune Encephalomyelitis Only in Female Mice

The prevalence of multiple sclerosis (MS) increases significantly with decreasing UV B light exposure, possibly reflecting a protective effect of vitamin D(3). Consistent with this theory, previous research has shown a strong protective effect 1,25-dihydroxyvitamin D(3) in experimental autoimmune encephalomyelitis (EAE), an MS model. However, it is not known whether the hormone precursor, vitamin D(3), has protective effects in EAE. To address this question, B10.PL mice were fed a diet with or without vitamin D(3), immunized with myelin basic protein, and studied for signs of EAE and for metabolites and transcripts of the vitamin D(3) endocrine system. The intact, vitamin D(3)-fed female mice had significantly less clinical, histopathological, and immunological signs of EAE than ovariectomized females or intact or castrated males. Correlating with reduced EAE, the intact, vitamin D(3)-fed female mice had significantly more 1,25-dihydroxyvitamin D(3) and fewer CYP24A1 transcripts, encoding the 1,25-dihydroxyvitamin D(3)-inactivating enzyme, in the spinal cord than the other groups of mice. Thus, there was an unexpected synergy between vitamin D(3) and ovarian tissue with regard to EAE inhibition. We hypothesize that an ovarian hormone inhibited CYP24A1 gene expression in the spinal cord, so the locally-produced 1,25-dihydroxyvitamin D(3) accumulated and resolved the inflammation before severe EAE developed. If humans have a similar gender difference in vitamin D(3) metabolism in the CNS, then sunlight deprivation would increase the MS risk more significantly in women than in men, which may contribute to the unexplained higher MS incidence in women than in men.

Risk of calcium oxalate nephrolithiasis in postmenopausal women supplemented with calcium or combined calcium and estrogen

BACKGROUND

Recent studies showed that postmenopausal women lost less bone mass when supplemented with calcium or estrogen therapy. However, the safety of the treatments in terms of the risk of calcium oxalate stone formation is unknown. We therefore conducted this study to determine the alteration in calcium oxalate supersaturation after calcium supplement or after combined calcium and estrogen therapy in postmenopausal osteoporotic women.

METHODS

Fifty-six postmenopausal women were enrolled in this study. All subjects were more than 10 years postmenopausal with vertebral or femoral osteoporosis by bone mineral density criteria. They were randomly allocated to receive either 625 mg of calcium carbonate (250 mg of elemental calcium) at the end of a meal three times a day (group A, n=26) or calcium carbonate in the same manner plus 0.625 mg/day of conjugated equine estrogen and 5 mg medrogestone acetate from day 1-12 each month (group B, n=30). The age (mean +/- S.E.M.) was 66.3 +/- 1.2 and 65.1 +/- 1.1 years, weight 54.1 +/- 1.2 and 55.3 +/- 2.1 kg, in group A and group B, respectively. Urine specimens (24-h) were collected at baseline and 3 months after treatment for the determination of calcium oxalate saturation by using Tiselius's index (AP(CaOx)) and calcium/citrate ratio.

RESULTS

After 3 months of treatment, there was no significant alteration from baseline for urinary excretion of calcium, citrate and oxalate. Urinary phosphate excretion was significantly reduced (6.3 +/- 0.7 vs. 5.1 +/- 0.7 mmol/day for group A and 8.2 +/- 0.9 vs. 5.8 +/- 0.7 mmol/day for group B, P<0.05), whereas net alkaline absorption was significantly elevated (10.1 +/- 3.6 vs. 20.1 +/- 4.4 meq/day for group A and 4.8 +/- 3.2 vs. 19.9 +/- 3.6 meq/day for group B, P<0.05). Calcium/citrate ratio and AP(CaOx) determined at baseline were not different from the corresponding values after treatment in both groups; calcium/citrate: 10.1 +/- 3.1 vs. 10.1 +/- 2.5 for group A and 9.3 +/- 1.8 vs. 11.9 +/- 2.5 for group B and AP(CaOx): 1.1 +/- 0.1 vs. 1.3 +/- 0.2 for group A and 1.2 +/- 0.2 vs. 1.1 +/- 0.1 for group B. There were eight and nine patients with high AP(CaOx), or >2, at baseline and after treatment, respectively.

CONCLUSIONS

Calcium supplement with a meal or combined calcium supplement and estrogen therapy is not associated with a significant increased risk of calcium oxalate stone formation in the majority of postmenopausal osteoporotic patients. Determination of urinary saturation for calcium oxalate after calcium and estrogen supplements, especially at the initial phase of treatment, may be helpful in the avoidance of nephrolithiasis.

Prevention of postmenopausal bone loss by low and conventional doses of calcitriol or conjugated equine estrogen

OBJECTIVES

Estrogen deficiency is the most common cause of postmenopausal osteoporosis and estrogen replacement is well known to retard postmenopausal bone loss. Calcium supplement alone is generally considered to be insufficient for the prevention of bone loss associated with estrogen deficiency while the role of calcitriol is unclear. In the present study we examined the efficacy different doses of estrogen or calcitriol in the prevention of postmenopausal bone loss in Thais.

METHODS

The subjects consisted of 146 Thai women no more than 6 years postmenopausal. The subjects were randomly allocated to receive 750 mg supplemental calcium alone, calcium and conjugated equine estrogen (CEE) at 0.3 or 0.625 mg, calcium and calcitriol at 0.25 or 0.5 microg daily. Those receiving CEE also took 5 mg medrogestone for 12 days each month. BMD at L2-4 and femoral neck were measured at baseline 1 year and 2 years after treatments. Data were expressed as mean +/- S.E.

RESULTS

Subjects on supplemental calcium alone had approximately 2.5% decreases in L2-4 (P < 0.05) and femoral BMD (P < 0.01) at 2 years. CEE (0.3 mg) resulted in 3.20 +/- 1.2% increase in vertebral BMD (P < 0.05) while no significant change in BMD was demonstrated at the femoral neck. Likewise, 0.625 mg of CEE induced 5.4 +/- 1.4% increase in vertebral BMD at 2 years (P < 0.001) without change in the femoral BMD. In regard to calcitriol, no significant change in vertebral or femoral BMD was demonstrated with either 0.25 or 0.5 microg calcitriol.

CONCLUSION

We concluded that calcitriol is effective in the prevention of early postmenopausal bone loss in Thais. It represents an option for the prevention of osteoporosis in postmenopausal women who are contraindicated for estrogen replacement.

Female sex hormone replacement therapy increases serum free 1,25-dihydroxyvitamin D3: a 1-year prospective study

OBJECTIVE

Currently, hormone replacement therapy is applied successfully to reduce post-menopausal bone resorption. However, the exact mechanism by which oestrogen exerts its effect has not yet been fully elucidated. In order to determine whether changes in the biologically active 1,25-dihydroxyvitamin D3 may be of importance in this process, the concentrations of both total and free 1,25-dihydroxyvitamin D3 in serum were assessed.

DESIGN

In 36 post-menopausal women the effect of hormone replacement therapy, with a combination of 17 beta-oestradiol and norethisterone acetate, on the serum levels of total and free 1,25-dihydroxyvitamin D3 was studied after 0, 3, 6 and 12 cycles.

MEASUREMENTS

The total concentration of 1,25-dihydroxyvitamin D3 in serum was assessed using a radioreceptor assay after diethylether extraction of the samples followed by paper chromatography. The free fraction of 1,25-dihydroxyvitamin D3 was measured using symmetric dialysis. The free 1,25 dihydroxyvitamin D3 concentration was calculated by multiplying the total concentration by the free fraction.

RESULTS

During therapy, mean serum total 1,25-dihydroxyvitamin D3 concentrations (+/- SD) were 106.4 pmol/l (+/- 27.5), 155.0 pmol/l (+/- 49.5), 176.7 pmol/l (+/- 70.0) and 161.1 pmol/l (+/- 55.3) at 0, 3, 6 and 12 cycles, respectively. Serum free 1,25-dihydroxyvitamin D3 concentrations were 68 fmol/l (+/- 22), 107 fmol/l (+/- 35), 120 fmol/l (+/- 43) and 108 fmol/l (+/- 37), respectively. Baseline values of both total and free 1,25-dihydroxyvitamin D3 were significantly lower than those during therapy at all time (P < or = 0.001).

CONCLUSION

Both the serum total 1,25-dihydroxyvitamin D3 and the serum free 1,25-dihydroxyvitamin D3 concentrations are increased during combined 17 beta-oestradiol and norethisterone acetate therapy for a year. Assuming that the free concentration 1,25-dihydroxyvitamin D3 reflects the biologically active fraction, this rise may in part explain the preventive effect of hormone replacement therapy on osteoporosis.

Modulation of intestinal vitamin D receptor by ovariectomy, estrogen and growth hormone

Age-related decline in intestinal calcium (Ca) absorption often occur in postmenopausal osteoporotic women. The impaired Ca absorption can be corrected by estrogen (E2) therapy. Growth hormone (GH) therapy has also been reported to increase intestinal absorption of calcium. Since 1,25-dyhydroxyvitamin D (1,25(OH)2D) is the primary regulator of calcium absorption, we explored whether the mechanisms by which E2 and GH enhance Ca absorption involves the vitamin D endocrine system. We measured serum 1,25(OH)2D concentrations and determined the binding characteristics of intestinal vitamin D receptors (VDRs) in four groups of female rats: sham operated (sham), ovariectomized (ovx), ovx + E2, and ovx + GH. Serum 1,25(OH)2D levels were 42.4 +/- 3.4 and 42.5 +/- 3.2 pg/ml in sham and ovx rats, respectively, and decreased by 63 and 34% (P < 0.001) in ovx + E2 and ovx + GH-treated rats, respectively. The numbers of total, unoccupied and occupied VDRs were 116.9 +/- 2.0, 72.1 +/- 1.1 and 44.8 +/- 1.9 fmol/mg protein, respectively, in sham operated rats, and decreased significantly following ovariectomy by 24, 27 and 19% (P < 0.01), respectively. E2 therapy not only significantly increased total, unoccupied and occupied VDRs above those of ovx rats by 55, 58 and 49% respectively, but it increased the levels above those of sham operated controls as well (P < 0.01). In contrast, GH administration prevented the decrease that occurred in ovx rats in the number of total and unoccupied VDRs (111.2 +/- 3.3; 72.6 +/- 1.4 fmol/mg protein, respectively), but it had no significant effect on the number of occupied VDRs. The dissociation constant (Kd) of intestinal VDRs was unaltered by ovariectomy, E2 and GH. We conclude that down regulation of intestinal VDRs may contribute to the Ca malabsorption that occurs in ovarian hormone deficient states such as postmenopausal osteoporosis, and that the stimulation of Ca absorption by E2 and GH may result, in part, from up regulation of intestinal VDRs.

Transdermal oestradiol gel in the treatment of the climacterium: a comparison with oral therapy

OBJECTIVE

To compare two doses of a transdermal oestradiol gel (Divigel/Sandrena) plus oral sequential medroxyprogesterone acetate (MPA) with oral oestradiol valerate plus oral sequential MPA (Divina/Dilena).

DESIGN

Two year, randomised, open-label, comparative study.

SETTING

Menopausal outpatient clinic in Helsinki.

SUBJECTS

Postmenopausal women with climacteric complaints or already using HRT.

INTERVENTIONS

(1) One gram gel containing 1 mg oestradiol for 3 months plus 20 mg oral MPA during the last 14 days; (2) 2 g gel containing 2 mg oestradiol for 21 days plus 10 mg oral MPA during the last 14 days; (3) 2 mg oestradiol valerate tablets for 3 weeks plus 10 mg oral MPA during the last 10 days. In all groups, each treatment period was followed by a 7-day medication-free interval.

MAIN OUTCOME MEASURES

Climacteric complaints, bleeding control, bone mineral density, biomarkers of bone metabolism, lipid profile, tolerability and safety.

RESULTS

With each preparation, climacteric complaints were significantly reduced and good bleeding control was obtained. In addition, maintenance of bone mineral density as well as a reduction of bone turnover was achieved in all groups. Lipid parameters showed no unfavourable changes. Continuation rates were similar in all groups with overall 74% of patients completing the first year, whereas 94% of patients who elected to continue completed the second year. Tolerability of the gel was good: only 1.7% of patients discontinued treatment due to skin irritation.

CONCLUSIONS

Transdermal oestradiol gel and oral oestradiol valerate tablets, used in combination with oral sequential MPA, are effective regimens of HRT in postmenopausal women. Transdermal oestradiol gel is an efficient, well-tolerated form of HRT.

Measurement of vitamin D and its metabolites (calcidiol and calcitriol) and their clinical significance

The serum concentration of vitamin D will only give information about the recent exposure to either nutritional vitamin D or to recent vitamin D production in the skin. Within hours vitamin D is removed from the circulation and reappears again a few hours later as 25(OH)D. Measurements of vitamin D therefore are not useful to judge the vitamin D status of man. Plasma concentrations of 25-hydroxyvitamin D (25(OH)D) are the best markers of imminent or existing vitamin D deficiency. Suboptimal vitamin D supply (or 25(OH)D plasma concentrations) are observed in most European countries and North America from November to April. Vitamin D substitution is recommended to persons with a serum concentration of 25(OH)D below 50 nmol/L (20 micrograms/L). Plasma concentrations of 1,25(OH)2D3 (calcitriol) depend mainly on renal function, concentrations of intact PTH and the supply of the organism with calcium and phosphate. High PTH, low calcium and low phosphate supply are the main stimulators of the production of calcitriol. Vitamin D substitution, or if necessary, therapy with active vitamin D metabolites or analogs, e.g. calcitriol or alfacalcidol, are often necessary in hypercalcemic persons with low serum concentrations of calcitriol, e.g. in patients with renal failure. Disorders with low or high vitamin D metabolite concentrations in serum are described in this paper.

Osteopenia and stable isotope ratios in bone collagen of Nubian female mummies

Stable carbon and nitrogen isotopes were analysed on bone collagen of 43 Sudanese Nubians from the X-Group period to test dietary hypotheses for the high frequency of osteopenia in this population. Stable carbon isotope ratios indicate that both normal and osteopenic individuals consumed the same mixed diet of C3 and C4 sources, which are assumed to have been constituted by the grain staples wheat/barley and sorghum/millet respectively. Females with osteopenia, however, have significantly elevated delta 15N values. The enrichment effect is greatest in the third and fifth decades of life, and is consistently patterned with microstructural and frequency differences previously reported by other researchers. It is suggested that delta 15N is reflecting differences in urea excretion and the renal processing and clearance of calcium and phosphorus. The study not only alerts us to the susceptibility of stable nitrogen isotopes to non-dietary (i.e. physiological) factors, but also identifies nitrogen isotope ratios as a possible new marker for osteopenia.

Effect of estrogen status on bone regulating hormones

The effect of surgically induced menopause and a subsequent estrogen monotherapy on the secretion of calciotropic hormones and serum minerals was evaluated in 11 perimenopausal menstruating women. In seven of them, plasma insulin growth factor-I was also assessed. In the 12th-16th week after bilateral oophorectomy, a decline of serum PTH (p < 0.01) and an increase of calcemia (p < 0.05), phosphatemia (p < 0.05), and IGF-I (p < 0.01) were documented. A subsequent transdermal estrogen substitution (100 micrograms/day for 6 weeks) returned these values to the preoperative range. However, neither the operation nor the estrogen treatment altered calcitonin secretion (basal and calcium stimulated), serum 1,25(OH)2, vitamin D3, or magnesium. The effectiveness of oophorectomy as well as compliance of estrogen substitution was documented by serum estradiol, FSH, and LH response. The results demonstrate a stimulating effect of estrogen on PTH secretion, secondary to an estrogen-induced reduction in plasma calcium. They further demonstrate an inhibitory effect on phosphatemia and IGF-I production, but no effect on calcitonin secretion and vitamin D metabolism.