Sarcopenia in women with hip fracture: A comparison of hormonal biomarkers and their relationship to skeletal muscle mass and function

High SHBG and Low Bioavailable Testosterone are Strongly Causally Associated with Increased Forearm Fracture Risk in Women: An MR Study Leveraging Novel Female-Specific Data

The effects of androgens on women's bone health are not fully understood. Mendelian randomization (MR) studies using sex-combined data suggest that sex hormone-binding globulin (SHBG) and bioavailable testosterone (BioT) causally affect bone traits. Given significant sex differences in hormone regulation and effects, female-specific MR studies are necessary. In the current study, we explored the causal relationships of SHBG, BioT, and total testosterone (TT) with forearm fracture (FAFx) risk in women using two-sample MR analyses. We utilized a unique female-specific FAFx outcome dataset from three European biobanks (UFO, HUNT, Estonian Biobank) comprising 111,351 women and 8823 FAFx cases, along with female-specific genetic instruments of SHBG, BioT, and TT identified in the UK Biobank. We also assessed bone mineral density (BMD) at the forearm (FA), femoral neck (FN), and lumbar spine (LS) using female-specific GWAS data from the GEFOS consortium. High SHBG (odds ratio per standard deviation increase (OR/SD): 1.53, 95% confidence intervals (CIs): 1.34-1.75), low BioT (OR/SD: 0.77, 0.71-0.84) and low TT (OR/SD 0.90, 0.83-0.98) were causally associated with increased FAFx risk. BioT was positively, and SHBG inversely, causally associated with especially FA-BMD, but also LS-BMD and FN-BMD, while TT was only significantly positively associated with FA-BMD and LS-BMD. We propose that endogenous androgens and SHBG are important for women's bone health at distal trabecular-rich bone sites such as the distal forearm and may serve as predictors for FAFx risk.

The Role of Osteokines in Sarcopenia: Therapeutic Directions and Application Prospects

Sarcopenia is an age-related disease in which muscle mass, strength and function may decline with age or can be secondary to cachexia or malnutrition and can lead to weakness, falls and even death. With the increase in life expectancy, sarcopenia has become a major threat to the health of the elderly. Currently, our understanding of bone-muscle interactions is not limited to their mechanical coupling. Bone and muscle have been identified as secretory endocrine organs, and their interaction may affect the function of each. Both muscle-derived factors and osteokines can play a role in regulating muscle and bone metabolism via autocrine, paracrine and endocrine mechanisms. Herein, we comprehensively summarize the latest research progress on the effects of the osteokines FGF-23, IGF-1, RANKL and osteocalcin on muscle to explore whether these cytokines can be utilized to treat and prevent sarcopenia.

The effect of sex hormones on skeletal muscle adaptation in females

Sex steroids, commonly referred to as sex hormones, are integral to the development and maintenance of the human reproductive system. In addition, male (androgens) and female (estrogens and progestogens) sex hormones promote the development of secondary sex characteristics by targeting a range of other tissues, including skeletal muscle. The role of androgens on skeletal muscle mass, function and metabolism has been well described in males, yet female specific studies are scarce in the literature. This narrative review summarises the available evidence around the mechanistic role of androgens, estrogens and progestogens in female skeletal muscle. An analysis of the literature indicates that sex steroids play important roles in the regulation of female skeletal muscle mass and function. The free fractions of testosterone and progesterone in serum were consistently associated with the regulation of muscle mass, while estrogens may be primarily involved in mediating the muscle contractile function in conjunction with other sex hormones. Muscle strength was however not directly associated with any hormone in isolation when at physiological concentrations. Importantly, recent evidence suggests that intramuscular sex hormone concentrations may be more strongly associated with muscle size and function than circulating forms, providing interesting opportunities for future research. By combining cross-sectional, interventional and mechanical studies, this review aims to provide a broad, multidisciplinary picture of the current knowledge of the effects of sex steroids on skeletal muscle in females, with a focus on the regulation of muscle size and function and an insight into their clinical implications. HighlightsFree testosterone, but not total testosterone, is associated with lean mass but not strength in pre- and post-menopausal females.Progesterone and estrogens may regulate muscle mass and strength, respectively, in females.Intra-muscular steroids may be more closely associated to muscle mass and strength, compared to systemic fractions.