Endocrine Abstracts

Objectives: Patients with chronic heart failure (CHF) almost universally complain of exercise intolerance due, in part, to alterations of skeletal muscle. In men, testosterone is an important determinant of muscle bulk and strength. Relative androgen deficiency in men with CHF could contribute to exercise intolerance. We studied the relationship between plasma levels of testosterone and measures of skeletal muscle bulk and strength and exercise capacity in men with CHF.

Methods: 48 men with stable CHF were studied. Plasma levels of total and bio-available testosterone were measured between 0800 and 0900. Skeletal muscle bulk was estimated from cross-sectional CT images of mid-thigh and mid-calf, using planimetry to determine muscle area. Strength was estimated from hand grip dynamometery. Exercise capacity was assessed using the incremental shuttle walk test. 20 subjects were subsequently randomised to receive testosterone (Sustanon100) or normal saline (1ml) by fortnightly intramuscular injection in a 3 month double-blind study.

Results: Mean total testosterone level was 15.3 ± 5.2nmol/L, bio-available testosterone was 4.6 ± 2.4nmol/L; ejection fraction was 33.6 ± 9.7%. The bio-available testosterone level correlated positively with muscle bulk and grip strength, although this only reached statistical significance with thigh muscle (r=0.49, p=0.028). Subjects with total testosterone <10nmol/L or bio-available testosterone <2.5nmol\/L tended to have smaller thigh muscle area (6307.6 ± 722.0mm² v 7321.8 ± 1449.7mm², p=0.059) and poorer exercise capacity (226.7 ± 109.1m v 318.0 ± 170.6m, p=0.06). Following testosterone treatment, there was a significant increase in exercise capacity (from 328 ± 174m to 419 ± 200m, p=0.01) but no change in measures of muscle bulk and strength.

Conclusion: There appears to be a positive relationship between endogenous bio-available testosterone and measures of skeletal muscle bulk and strength in men with CHF. Administration of testosterone may improve exercise capacity in these patients.