Sir: Abundant evidence links decreased bone density with oestrogen-deficient status in women, and increases in bone density have been noted after oestrogen therapy [7]. Osteopenia in male hypogonadism, especially in adolescent boys, and concomitant androgen therapy has been only rarely reported [3, 5]. Recently, we investigated the effect of testosterone therapy on bone density in a boy with hypogonadotropic hypogonadism.
A 17-year-old boy with Tanner stage I external genitalia was diagnosed as having an idiopathic isolated gonadotropin deficiency based upon the results of both a luteinizing hormone-releasing hormone test and a human chorionic gonadotropin (HCG) loading test. There was no anosmia. Plasma testosterone response to HCG stimulation (HCG 3000 units/m 2 for 3 days) rose from 10 ng/dl (basal level) to 90 ng/dl (peak level). Plasma somatomedin C concentration was 1.5U/ml (normal = 1.35-3.0). The patient's skeletal age was 13 years. Serum calcium, phosphorus, carboxyterminal parathyroid hormone, calcitonin, and vitamin D metabolites (25-hydroxy vitamin D and 1,25-dihydroxy vitamin D) were all within normal limits.
Bone mineral density evaluated by single-photon absorptiometry at the non-dominant distal radius was decreased: 0.50g/cm 2 (normal 0.59 +_ 0.05). Testosterone enanthate 125 mg every 3 weeks (total four times) led to a significant increase in bone density to 0.57 g/cm 2.
During puberty, a marked increase in bone density occurs and this is thought to be due to increased sex steroid secretion [1, 2, 4, 6]. Androgen deficiency during puberty seems to be a risk factor for osteopenia in adolescent boys and young male adults [1, 4, 5]. As shown by our patient, testosterone replacement at the appropriate age stimulates the pubertal increase in bone density and increases the skeletal resistance to mechanical forces.