A double blind, placebo controlled study of the effects of low dose testosterone undecanoate on the growth of small for age, prepubertal boys

Objective-To assess whether very low doses of testosterone can accelerate growth without an undue advance in bone age in prepubertal boys with constitutional delay of growth. Subjects-23 prepubertal boys aged 11-14 years with height at or below the third centile for chronological age. Design-Randomised, double blind trial comparing oral testosterone undecanoate 20 mg once daily versus placebo for six months. The 18 months' observation period of each subject comprised a six month pretreatment period, followed by a six month treatment (testosterone undecanoate or placebo) period, and a six month period after terniination of treatment. Outcome measures-At intervals of six months standing and sitting height were measured. Bone age, pubertal stage, weight, and lean body mass were also determined. Growth hormone, luteinising hormone, and follicle stimulating hormone secretion and testosterone concentration were measured before, after, and six months after treatment. Results-Boys taking testosterone undecanoate (n= 1) showed a significantly greater height velocity (mean (SEM) 5·84 (0·53) cm/year) and sitting height velocity (3·54 (0·57) cm/year) during treatment than the placebo treated boys (n= 12, height velocity=3·38 (0·22) cm/year, sitting height velocity= 1·58 (0·19) cm/year. There were no significant differences between the groups regarding changes in growth hormone, gonadotrophins, testosterone, or dihydrotestosterone concentrations. Bone age was not advanced significantly more rapidly in either group. Conclusions-There is accelerated gain in height during six months of treatment with low dose testosterone undecanoate, without a significantly greater rise in bone age compared with controls. Testosterone undecanoate is a safe, well tolerated, and effective treatment in the management of constitutional delay of growth.