Inhibin A and B in peri- and postmenopause

Postmenopausal HRT and tibolone in relation to muscle strength and body composition

OBJECTIVES

Sarcopenia, the loss of muscle mass with age, has a great impact on physical function, and especially in postmenopausal women, who experience a greater decline in muscle strength than do men of similar age. Conventional hormone replacement therapy (HRT) may diminish this loss of muscle strength and may even increase muscle strength. However, HRT is not currently promoted for this indication because of its negative side effects, which is why tibolone, a synthetic steroid with oestrogenic, progestogenic, and androgenic activity, may be an alternative option. The aim of this article was to review data on the effect of HRT and tibolone on muscle strength and body composition in postmenopausal women.

METHODS

Medline, Pubmed, Embase, and Sumsearch were searched for articles on the effect of HRT and tibolone on muscle strength and body composition, using the Mesh terms hormone replacement therapy and clinical trial combined with muscle strength or body composition. Tibolone was added as search term with clinical trial and muscle strength or body composition.

RESULTS

Three of five randomized controlled trials reported a significant positive effect of HRT on muscle strength but not on body composition. Tibolone significantly increased handgrip strength and isometric knee extension strength in one randomized placebo-controlled, double-blind trial and increased mean knee extensor strength in one cross-sectional study. Tibolone also increased the lean body mass and decreased the accumulation of body fat.

CONCLUSIONS

HRT and tibolone increase muscle strength. Unlike HRT, tibolone also increases lean body mass and significantly reduces the total body fat content. Further research is recommended to determine whether tibolone is a safe treatment for sarcopenia.

Greater inhibition of the pituitary--ovarian axis in oral contraceptive regimens with a shortened hormone-free interval

OBJECTIVE

Our objective was to test the hypothesis that shortening the hormone-free interval (HFI) between cycles of 21 days of oral contraceptives (OCs) reduces pituitary secretion of gonadotropins and ovarian production of estradiol and inhibin-B.

DESIGN

We used a prospective trial design comparing the standard 7-day HFI and shortened HFI during cycles, with an OC containing 0.03 mg of ethinyl estradiol and 3 mg of drospirenone.

METHODS

Twelve current OC users initially utilized an OC in the standard fashion, with 21 days of active pills and a 7-day HFI, followed by 21 days of active pills with randomization to either a 3-day or a 4-day HFI. Nine daily blood samples were obtained for the measurement of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol and inhibin-B, beginning with active pill 21 days before each HFI of the two cycles. Analysis of variance was used to compare hormones for 9 days bracketing the standard 7-day HFI and to compare, within individuals, the 7-day HFI and the subsequent shortened HFI.

RESULTS

During the 7-day HFI, all four hormones significantly (p>.001) increased from baseline. FSH increased beginning on HFI Day 4, inhibin-B increased beginning on HFI Day 5, and LH and estradiol increased beginning on HFI Day 6. Subjects randomized to the 3-day or the 4-day HFI did not differ with regard to age and body size (p=.88) or initial hormone level (p=.67). Greater pituitary and ovarian suppression was seen with the shortened HFI for all four hormones (p<.001). Hormone levels in the 7 days after the last active pill of the second cycle did not differ (p>.4) between the 3-day and the 4-day HFI groups.

CONCLUSIONS

Shortening the HFI from 7 days to 3 or 4 days blunts increases in the pituitary-ovarian axis during cycles of OC use.

Significance of inhibin in reproductive pathophysiology and current clinical applications

The human reproductive process is regulated by complex mechanisms that involve many organs, including the brain, gonads and endocrine system. It has been more than 70 years since the name 'inhibin' was used to describe a substance produced in the gonads that negatively regulates pituitary secretion. Inhibin B controls FSH secretion via a negative feedback mechanism. It is a glycoprotein hormone secreted by the Sertoli cells of the testis and granulosa and theca cells of the ovary. Serum inhibin B concentrations are positively related to testicular volume and sperm counts. Current understanding of inhibin physiology and pathology in the human suggests that inhibin B may be of importance as a marker of Sertoli cell function in men with infertility and as a prognostic indicator in women undergoing ovulation induction therapy. Inhibin concentrations are elevated in patients with granulosa cell tumours and in post-menopausal women with mucinous ovarian cancers. Immunoreactivity against the inhibin alpha-subunit was identified in all cases of adrenal cortical adenoma and carcinoma, and levels are suppressed in the malignant prostate disease. This article discusses the structure, regulation and clinical use of inhibin and other related substances.

Evaluation of the applicability of HRT as a preservative of muscle strength in women

OBJECTIVES

To review the studies that have been undertaken on the effects of postmenopausal hormone replacement therapy (HRT); especially oestrogen (+progestin) regimens on the preservation of muscle strength. Current knowledge of the mechanisms and actions of steroid- and sex hormones on skeletal muscle tissue will be used in an attempt to clarify the mechanism of action of a possible effect. The objective is to arrive at an agreement on whether or not postmenopausal oestrogen administration has a positive influence on skeletal muscle tissue.

METHODS

Peer-reviewed publications were assessed.

RESULTS

An age-related decrement in muscle strength can be found in both men and women. However, in women, an extra decline can be observed around the time of menopause. A possible relationship between the additional diminution in muscle strength and altered hormone concentrations after the onset of menopause has been suggested. Since women nowadays spend one-third of their life postmenopausal, it is extremely important to keep the decline in muscle mass as small as possible. Besides the continuation of a physically active lifestyle, HRT was suggested to serve as a protective mechanism. Although, the usefulness of HRT as a preservative of muscle strength appeared controversial.

CONCLUSIONS

Skeletal muscle strength is sensitive to training up to a high age, though continuation of physical activity does not appear to protect skeletal muscles completely from age-related decrements. Therefore, the development of another preventive method would be useful. Considering the present knowledge it has all the hallmarks that HRT can be a useful tool in the maintenance of muscle strength in postmenopausal women. None the less, further research is necessary to endorse this theory.