The effect of menopause and hormone replacement therapy on bone alkaline phosphatase

Hormones and bone health in postmenopausal women

Although it has been known for some time that estrogen deficiency is a major pathogenetic factor for osteoporosis related fractures among postmenopausal women, the capability of estrogen (with or without a progestin) to prevent fractures has often been questioned. The publication of the data from the two hormone clinical trials of the Women's Health Initiative lays that discussion to rest. In both studies what have been considered a standard dose of conjugated estrogen with or without medroxyprogesterone acetate significantly reduced the risk of all fractures, including clinical vertebral fractures and hip fracture, in a population of postmenopausal women, average age 63 yr, not selected for osteoporosis by BMD. These results are particularly impressive given the difficulty of finding a fracture benefit in lower risk populations with other anti-resorptive agents. Surrogate data on lower doses of hormone therapy suggest a fracture benefit would be seen if studies were to be done. The other outcomes in WHI make it important to define appropriate clinical guidelines for use of hormone therapy for prevention of fractures in postmenopausal women.

Piperazine oestrone sulphate and interrupted norethisterone in postmenopausal women: effects on bone mass, lipoprotein metabolism, climacteric symptoms, and adverse effects

OBJECTIVE

To compare the effects of two doses of piperazine oestrone sulphate combined with interrupted norethisterone, with that of oestradiol continuously combined with norethisterone acetate, and with placebo, in postmenopausal women.

DESIGN

A prospective randomised trial.

PARTICIPANTS

Two hundred postmenopausal women.

SETTING

Monocentre study with expertise in osteoporosis.

METHODS

The participants were randomly assigned to two years of treatment with alternating three-day cycles of 1.5 mg of piperazine oestrone sulphate plus 0.7 mg of norethisterone (highEP), or alternating three-day cycles of 0.75 mg of piperaine oestrone sulphate plus 0.35 mg of norethisterone (lowEP), or 2 mg of 17beta-oestradiol continuously combined with 1 mg of norethisterone acetate (E2+NETA), or placebo.

MAIN OUTCOME MEASURES

Change in bone mineral density, lipoprotein metabolism, climacteric symptoms, and adverse effects.

RESULTS

One hundred and twenty-one women completed the study. Spinal bone mineral density was increased about 9% over two years by E2+NETA, about 6% by highEP, 4% by lowEP, but remained unchanged in the placebo group. The same pattern was seen in the hip and forearm. All hormone regimens decreased markers of bone turnover and alleviated climacteric symptoms. Serum lipoproteins decreased by about 10% in all hormone groups.

CONCLUSIONS

All hormone regimens studied prevented bone loss completely and lowered serum lipids.

Measurement of serum bone-specific alkaline phosphatase activity in cynomolgus macaques

Serum levels of bone-specific alkaline phosphatase activity (B-ALP) in cynomolgus monkeys were evaluated as an index of elevated bone turnover following ovariectomy. The enzyme immunoassay 96-well microtiter plate B-ALP assay, developed by Metra Biosystems (Mountain View, CA) for human use, was employed and compared with a standard automated assay measuring total serum levels of alkaline phosphatase activity (T-ALP). The B-ALP assay was first validated for use in these monkeys. Ovariectomy led to increased bone turnover as indicated by approximately 2-fold higher activity in both assays and this elevation was inhibited by daily estradiol administration. Although both assays provided generally similar results, several monkeys were observed to have greatly elevated values of T-ALP but not B-ALP. This discrepancy is believed to result from high levels of the liver isoform of alkaline phosphatase in monkeys with hepatic dysfunction, which are not detected by the B-ALP assay.

Monofluorophosphate combined with hormone replacement therapy induces a synergistic effect on bone mass by dissociating bone formation and resorption in postmenopausal women: a randomized study

Sodium fluoride stimulates bone formation and has been used to treat osteoporosis for decades despite debate about the antifracture efficacy. Hormone replacement therapy (HRT) results in only modest increases in bone mineral density (BMD). However, for women with low bone mass, the ideal therapy should not only inhibit bone resorption but simultaneously stimulate bone formation to increase bone mass above the fracture threshold. We thus performed a randomized, double-blind, placebo-controlled intervention study to prospectively investigate the effect of a low dose of fluoride, in combination with HRT, on BMD and biochemical markers of bone turnover. One hundred healthy postmenopausal women (60-70 yr old) were thus randomly assigned to: 1) HRT [transdermal 17beta-estradiol, releasing 50 microg/day; plus oral norethisterone acetate (NETA), 1 mg/day]; or 2) oral monofluorophosphate (MFP; equivalent to fluoride, 20 mg/day); or 3) HRT+MFP; or 4) placebo, for 96 weeks. All participants received a calcium supplement of 1000 mg/day. Sixty-eight women completed the study. We found a pronounced, linear increase in spinal BMD during treatment with HRT+MFP [11.8% (1.7% SEM)], which was significantly greater than the increase in the HRT group [4.0% (0.5% per yr); P < 0.05]. MFP produced a smaller increase [2.4% (0.6% per yr)], whereas there was no change in the placebo group [0.0% (0.5% SEM)]. Similar changes were found at the other skeletal sites (distal forearm, hip, and total body). Markers of bone formation showed a fall in the HRT group, which was significantly more pronounced than in the combined HRT+MFP group. A nonsignificant increase was found in the MFP group, whereas the placebo group showed a decrease caused by calcium treatment. The marker of bone resorption decreased significantly more in the HRT and the HRT+MFP groups than in the placebo group but tended to increase in the MFP group. In conclusion, this study shows, by use of biochemical markers of bone turnover, that bone resorption and formation may be dissociated, as a result of actions of two compounds with diverging effects on bone turnover. Furthermore, the synergistic effects of relatively low doses of the compounds suggested statistically and clinically significant increases in trabecular and probably also cortical bone. Adverse effects were relatively rare and mild.

Practical clinical application of biochemical markers of bone turnover: Consensus of an expert panel

Biochemical markers of bone turnover have emerged as powerful tools to aid in managing osteoporosis. The newer bone markers have been intensively studied for more than a decade. As a result, we can now confidently report their clinical utility in assessing risk of rapid bone loss and fracture, and monitoring therapy in postmenopausal women with or at risk of osteoporosis. In this review, we will provide a comprehensive foundation for this utility. While there are still questions remaining to be answered, bone marker technology has matured to play an essential role in patient management. We will describe, in practical terms, how bone markers can be appropriately incorporated into clinical practice today.

The menopause transition

New paradigms for the study of menopause will increase our understanding of whether symptoms, syndromes, and chronic diseases are associated with menopause. Rather than considering menopause as a discrete event, it has become clear that the menopause transition takes place over many years. Although this realization is central to our understanding of menopause, it is difficult to measure the temporal pattern of changes in hormones and their relation to concurrent or subsequent health-related events. The model of hormonal changes at the time of the transition has been expanded to include not only declines in estrogen but changes in a broader range of hormones, including the potential role of androgens. New models are attempting to account for the pattern and frequency of changes in hormone levels. Another level of complexity is contributed by the expansion of the menopause model to include comorbid medical and psychiatric conditions, environmental influences, and behaviors as covariates that influence the expression of menopause-related events. Although this more complicated paradigm makes the conduct of menopause research more challenging, it is also likely to elucidate previously confusing data, as the proper understanding of potentially complex exposures, effect modifiers, and confounders is more likely to provide clearer answers to critical research questions.