Biochemical short-term changes produced by hormonal replacement therapy

Free 25(OH)D and the Vitamin D Paradox in African Americans

CONTEXT

African Americans have a lower total serum 25-hydroxyvitamin D [25(OH)D] but superior bone health. This has been referred to as a paradox. A recent publication found that free serum 25(OH)D is the same in black and white individuals. However, the study was criticized because an indirect method was used to measure free 25(OH)D. A direct method has recently been developed.

OBJECTIVE

We hypothesized that although total serum 25(OH)D is lower in African Americans, free serum 25(OH)D measured directly would not differ between races.

DESIGN

White and black healthy postmenopausal women were matched for age and body mass index. Serum total 25(OH)D, PTH, 1,25-dihydroxyvitamin D, vitamin D binding protein (VDBP), and bone density were measured. Measurement of free 25(OH)D was carried out using an ELISA.

SETTING

The study was conducted at an ambulatory research unit in a teaching hospital.

OUTCOME

A cross-racial comparison of serum free 25(OH)D was performed.

RESULTS

A propensity match resulted in the selection of a total of 164 women. Total 25(OH)D was lower in black women (19.5 ± 4.7 vs 26.9 ± 6.4 ng/mL), but a direct measurement of free 25(OH)D revealed almost identical values (5.25 ± 1.2 vs 5.25 ± 1.3 ng/mL) between races. VDBP was significantly lower in blacks when using a monoclonal-based ELISA but higher with a polyclonal-based ELISA. Serum PTH, 1,25-dihydroxyvitamin D, and bone density were higher in African Americans.

CONCLUSIONS

Free serum 25(OH)D is the same across races despite the lower total serum 25(OH)D in black women. Results comparing VDBP between races using a monoclonal vs a polyclonal assay were discordant.

Responses of parathyroid hormone to vitamin D supplementation: a systematic review of clinical trials

The beneficial bone effects of vitamin D supplementation have been attributed to suppression of secondary hyperparathyroidism by 25-hydroxyvitamin D (25-OHD) levels at least 50nmol/l. In this systematic review, we have analyzed the results of 52 clinical trials, including 72 intervention groups and 6290 patients, on vitamin D supplementation in order to evaluate the experimental evidence and the effects of age and chronic immobility on responses of parathyroid hormone (PTH). The papers for this systematic review were selected through a search in PubMed and through a review of the reference lists of articles. Negative logarithmic (R(2)=0.318, p<0.001) and linear (R(2)=0.294, p<0.001) correlations were found between 25-OHD and PTH levels, when all pre- and post-trial values were scattered. Negative linear (R(2)=0.385, p<0.001) and logarithmic (R(2)=0.406, p<0.001) correlations were also found between the changes in 25-OHD and PTH levels. Age correlated negatively with changes in PTH (r=-0.476, p<0.001). The vitamin D supplementation of the chronically immobile patients resulted in a smaller decrease in PTH levels (-8.4 vs. -17.4%, p<0.001) despite a larger increase in 25-OHD levels (187.2% vs. 109.8%, p<0.001). According to the multiple regression analysis the changes in PTH were independently predicted by pre-trial PTH, changes in 25-OHD, age and chronic immobility, explaining 53.2% (R(2)=0.532) of the variation. This meta-analysis shows that responses of PTH to vitamin D supplementation are not only determined by the baseline PTH levels and changes in vitamin D status, but also by age and mobility of the patients. Our results also suggest that PTH decreases quite linearly during vitamin D supplementation at any given 25-OHD level. Longitudinal vitamin D supplementation studies on populations with wide range of mobility and age are needed to further elucidate their confounding effects. In determining the sufficient doses of vitamin D supplementation and adequate 25-OHD levels, these confounding effects and the inter-individual variation in responses of PTH to vitamin D supplementation should be taken into account.

Diagnostic Considerations in the Measurement of Human Chorionic Gonadotropin in Aging Women

Background: Human chorionic gondadotropin (hCG) screening tests are performed on nearly all female patients of childbearing age before any medical intervention. Although older women usually have negative hCG test results, positive results do occur and may cause clinical confusion. We examined changes with age in serum hCG concentrations in nonpregnant women and investigated the use of serum follicle-stimulating hormone (FSH) measurements as an aid to interpreting higher than expected (“positive”) hCG results.

Methods: We used 240 serum specimens for each of 4 female cohorts: pregnant, ≥18 years; nonpregnant, 18–40 years (premenopausal); nonpregnant, 41–55 years (perimenopausal); and nonpregnant, &gt;55 years (postmenopausal). Patients were excluded if they had an ectopic pregnancy, a history of trophoblastic disease or a germ-cell tumor, or if no chart was available for review. Quantitative hCG and FSH tests were performed on each specimen.

Results: Serum hCG concentrations in nonpregnant women increased with the age of the women. hCG results were higher and significantly different (P &lt;0.0001) for nonpregnant women &gt;55 years (&lt;2.0 to 13.1 IU/L) compared with nonpregnant women 18–40 years (&lt;2.0 to 4.6 IU/L) and 41–55 years (&lt;2.0 to 7.7 IU/L). Nineteen nonpregnant women &gt;40 years of age had hCG concentrations ≥5.0 IU/L, all with an FSH concentration &gt;32.4 IU/L. The highest FSH concentration in pregnancy was 7.3 IU/L.

Conclusions: Serum hCG increases with age in nonpregnant women. A cutoff of 14.0 IU/L should be used when interpreting hCG results in women &gt;55 years of age. Pregnancy is unlikely in perimenopausal women 41–55 years of age with an hCG between 5.0 and 14.0 IU/L if serum FSH is &gt;20.0 IU/L.

Effects of eccentric exercise training on cortical bone and muscle strength in the estrogen-deficient mouse

The purpose of this study was to determine whether eccentrically biased exercise training could attenuate changes in muscle and bone function associated with estrogen deficiency in the mouse model. Four groups of ICR mice were used: control (Con), sham ovariectomized (Sham), ovariectomized (OVX), and ovariectomized + high-force resistance training (OVX+Train). All groups except Con were implanted with a nerve cuff surrounding the peroneal nerve to stimulate the left ankle dorsiflexors. Training consisted of 30 stimulated eccentric contractions of the left ankle dorsiflexors at approximately 150% of peak isometric torque every third day for 8 wk. After the training period, groups were not significantly different with regard to peak torque or muscle size. However, the tibial midshaft of the trained leg in the OVX+Train mice exhibited greater stiffness (+15%) than that in the untrained OVX mice, which could not be explained by changes in cross-sectional geometry of the tibia. Scaling of bone mechanical properties to muscle strength were not altered by ovariectomy or training. These data indicate that eccentric exercise training in adult mice can significantly increase bone stiffness, despite the absence of ovarian hormones.

Vitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosis

We attempted to investigate whether vitamin K2 (menatetrenone) treatment effectively prevents the incidence of new fractures in osteoporosis. A total of 241 osteoporotic patients were enrolled in a 24-month randomized open label study. The control group (without treatment; n = 121) and the vitamin K2-treated group (n = 120), which received 45 mg/day orally vitamin K2, were followed for lumbar bone mineral density (LBMD; measured by dual-energy X-ray absorptiometry [DXA]) and occurrence of new clinical fractures. Serum level of Glu-osteocalcin (Glu-OC) and menaquinone-4 levels were measured at the end of the follow-up period. Serum level of OC and urinary excretion of deoxypyridinoline (DPD) were measured before and after the treatment. The background data of these two groups were identical. The incidence of clinical fractures during the 2 years of treatment in the control was higher than the vitamin K2-treated group (chi2 = 10.935; p = 0.0273). The percentages of change from the initial value of LBMD at 6, 12, and 24 months after the initiation of the study were -1.8 +/- 0.6%, -2.4 +/- 0.7%, and -3.3 +/- 0.8% for the control group, and 1.4 +/- 0.7%, -0.1 +/- 0.6%, and -0.5 +/- 1.0% for the vitamin K2-treated group, respectively. The changes in LBMD at each time point were significantly different between the control and the treated group (p = 0.0010 for 6 months, p = 0.0153 for 12 months, and p = 0.0339 for 24 months). The serum levels of Glu-OC at the end of the observation period in the control and the treated group were 3.0 +/- 0.3 ng/ml and 1.6 +/- 0.1 ng/ml, respectively (p < 0.0001), while the serum level of OC measured by the conventional radioimmunoassay (RIA) showed a significant rise (42.4 +/-6.9% from the basal value) in the treated group at 24 months (18.2 +/- 6.1% for the controls;p = 0.0081). There was no significant change in urinary DPD excretion in the treated group. These findings suggest that vitamin K2 treatment effectively prevents the occurrence of new fractures, although the vitamin K2-treated group failed to increase in LBMD. Furthermore, vitamin K2 treatment enhances gamma-carboxylation of the OC molecule.

Effects on bone of oral hormone replacement therapy initiated 2 years after ovariectomy in young adult monkeys

The purpose of this study was to determine the effects of oral estrogen replacement therapy with conjugated equine estrogens (CEE), alone or in combination with continuous medroxyprogesterone acetate (MPA), on lumbar spine bone mineral content (BMC) and density (BMD) and on serum chemistries in ovariectomized cynomolgus monkeys when therapy is initiated following a 2 year hypoestrogenic period. Study design was done in the form of a randomized, placebo-controlled, nonhuman primate paraclinical trial. Monkeys were subjects in an experiment designed to study the effects of a lipid-lowering diet combined with hormone replacement therapy on atherosclerosis. Initially, they were ovariectomized and fed a high-fat diet for 24 months. They were then were allocated to three treatment groups by stratified randomization and were fed a diet containing reduced dietary fat for an additional 28 months. Treatment groups consisted of: (1) an untreated group (ovx, n = 24); (2) a CEE-treated group (CEE, n = 19); and (3) a CEE plus continuous MPA group (CEE + MPA, n = 20). Lumbar spine BMC and BMD values were measured by dual-energy x-ray absorptiometry at baseline and 4, 10, 16, 22, and 28 months of treatment. Serum chemistries were relevant to bone metabolism at 22 and 28 months. Rates of gain in BMC and BMD were greater (p < 0.05) in hormone-supplemented animals (groups 2 and 3) than in untreated ovx animals during the first 16 months of treatment, resulting in increased BMC and BMD measurements in these groups. Serum markers of bone metabolism were significantly lower (p < 0.05) in the hormone-treated groups (groups 2 and 3) compared with ovx animals after 22 and 28 months of treatment, indicating reductions in bone turnover rate. Oral estrogen replacement with CEE at doses similar to those taken by women leads to significantly increased BMC and BMD in monkeys, even when therapy is begun 2 years after ovariectomy. Most of the increase occurred during the first 16 months of treatment. The addition of MPA to the CEE regimen provided no additional benefit.

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

Osteoporosis is a common disorder in postmenopausal women, which is probably due to decreased ovarian function. Currently, hormone replacement therapy (HRT), involving administration of estrogen and progestogen, is successfully applied to reduce bone resorption. We studied the effect of HRT on 23 postmenopausal women. This consisted of a combination of 17 beta-estradiol and dydrogesterone, on the serum level of 1,25-dihydroxyvitamin D (1,25(OH)2D) after 0, 6, 12, and 24 months. We found mean serum concentrations (+/- SD) of 1,25(OH)2D of 130.5 pmol/liter (46.1), 152.7 pmol/liter (45.1), 170.8 pmol/liter (64.0), and 155.2 pmol/liter (59.7), respectively. The baseline values in these women were found to be significantly lower than those during therapy (P < or = 0.005). No statistically significant differences were observed when comparing the estrogen-only phase with the combined estrogen-progestogen phase. It is concluded that HRT results in an increase in the serum 1,25(OH)2D concentration which lasts for at least 2 years. This increase may partly explain the preventive effect of HRT on osteoporosis. Furthermore, these results suggest that dydrogesterone does not influence the estrogen-induced changes in serum 1,25(OH)2D concentration.

Bone functional changes in intact, ovariectomized, and ovariectomized, hormone-supplemented adult cynomolgus monkeys (Macaca fascicularis) evaluated by serum markers and dynamic histomorphometry

Several parameters of bone mass and function were investigated in three experiments involving intact, ovariectomized, or hormone-supplemented ovariectomized female cynomolgus monkeys. Ovariectomized animals had increased serum levels of alkaline phosphatase and acid phosphatase compared with intact and hormone-supplemented animals. Vertebral bone mass measured ex vivo by dual-photon absorptiometry was reduced by 11-19% in ovariectomized animals compared with intact and hormone-supplemented animals. The most dramatic effects observed with ovariectomy were markedly increased (30-60%) bone formation rates in vertebral cancellous bone, primarily caused by higher activation frequency of basic multicellular units of bone. In addition, combined resorption and reversal periods were decreased and formation period increased in untreated ovariectomized animals. Changes in static histomorphometry parameters were less dramatic, cancellous bone volume being 1-14% lower in ovariectomized animals compared with intact or ovariectomized hormone-supplemented animals. The data indicate that changes in bone resorption are primarily responsible for the lower bone mass of estrogen deficiency and increased bone mass in hormone-supplemented animals. Bone changes in ovariectomized cynomolgus monkeys resemble those in women after menopause and similarly respond positively to hormone supplementation. As such, cynomolgus monkeys are an excellent model for studying the basic mechanisms of osteoporosis and for the development of suitable therapeutic regimens.