Abstract and Introduction
Objective: To explore the associations between endogenous testosterone blood concentrations and muscle mass, strength and performance in community dwelling women.
Design, Patients and Measurements: Online databases, including Ovid MEDLINE, EMBASE and Web of Science, were searched for observational studies, with at least 100 female participants, reporting associations between endogenous testosterone blood concentrations and muscle mass, strength and performance. The findings were synthesized in a narrative review. Heterogeneity in study design and analysis precluded a meta-analysis.
Results: Of the 36 articles retrieved for full-text review, 10 met the inclusion criteria. Eight studies were cross-sectional, 1 longitudinal and 1 provided both cross-sectional and longitudinal data. Testosterone was measured by liquid chromatography-tandem mass spectrometry in two studies and by immunoassay in 8. An association between total testosterone and muscle mass, strength or performance in women was not found. The studies of calculated free or bioavailable testosterone and lean muscle mass reported a positive association, but no association was reported for muscle strength or performance. Each included study was limited by a high risk of bias in at least one assessed domain.
Conclusions: This review does not support an association between testosterone and muscle mass, strength or performance in women. This, together with the reported associations between free or bioavailable testosterone and muscle mass should be interpreted cautiously due to the predominant use of immunoassay and the inaccuracy of calculated variables. Additionally, biological significance of nonprotein bound testosterone has not been established. Further studies examining the relationship between precisely measured testosterone and muscle mass and function in women are required.
The maintenance of muscle strength in women as they age is important, especially after menopause. Loss of muscle mass and strength are well-described components of sarcopenia,[1,2] and contribute to poor physical functioning, and increase the risk of falls and fractures.[1,3,4] Muscle mass also influences metabolic health, with decreased skeletal muscle mass predisposing to insulin resistance and development of type 2 diabetes mellitus. These consequences of diminished muscle mass and strength have broad physical and psychological health implications, and may ultimately result in loss of independence and the need for formalized care.[1,6]
While exercise and weight training are known to help maintain muscle health in women as they age, sex hormones may also play an important role. Testosterone has anabolic actions in muscle, directly through androgen receptors and indirectly via conversion to estradiol. However, the association between endogenous testosterone blood concentrations, including total testosterone, estimated nonprotein bound (hereafter referred to as 'free') testosterone or non-sex hormone binding globulin (SHBG) bound ('bioavailable') testosterone and skeletal muscle health in women is less well characterized. Evidence for a contribution of testosterone to skeletal muscle health in women could potentially justify further investigation into the use of exogenous testosterone as muscle conserving therapy.
The objective of this systematic review was to examine the published literature to determine whether there is evidence for an association between endogenous testosterone blood concentrations and muscle mass, as well as measures of muscle strength and performance, in women.
Clin Endocrinol. 2023;98(4):587-602. © 2023 Blackwell Publishing