Testosterone in Duchenne muscular dystrophy: effects on puberty and growth

Testosterone therapy is recommended for management of puberty from the age of 12 years in boys with Duchenne muscular dystrophy (DMD). Height measurement is problematic in these adolescent boys as lower limb contracture can be common and estimated height from segmental body part measurements may over-estimate height.

Bone growth was assessed using metacarpal and phalangeal measurements from hand radiographs. Raw length measurements were converted to Z-scores based on published normative data and compared by calculating the mean of each patient as 'composite bone length Z-score'. Biochemical data was also collected to monitor the safety of testosterone therapy.

A total of 22 boys with DMD on daily glucocorticoid were included in the study. Mean age at commencement of testosterone therapy was 14.05 (SD 1.20). 13 boys were commenced on intramuscular testosterone therapy and nine were commenced on topical testosterone therapy. At baseline, 20/22 (91 %) were pre-pubertal (G1). At follow-up, 16/22 (77.3 %) were at early stages of puberty (G2 or G3) and 6/22 (22.7 %) were at late stages of puberty (G4 or G5). At baseline and follow up, composite bone length Z-scores for chronological age were significantly lower than zero, -2.7 (SD 1.07) (p<0.001 vs. zero) and -3.3 (SD 1.17), (p<0.001 vs. zero), respectively. There were no statistically significant differences between the topical and IM group at baseline (p=0.61) or 1 year (p=0.40).

Measurements of metacarpophalangeal bone length confirms that testosterone therapy enhanced long bone growth in boys with DMD but does not achieve full catch-up growth. Both IM and topical testosterone effectively promote secondary sexual characteristics with no significant side effects.