We have studied clinical and endocrine parameters in a group (group A) of forty men referred to us because of persistent idiopathic gynaecomastia (of more than 18 months duration), before and during the administration of percutaneous dihydrotestosterone (DHT). The endocrine parameters (testosterone (T), 17 β-oestradiol (E2), DHT, gonadotrophins (FSH and LH) and prolactin (PRL)), were compared to those of control groups of 12 healthy men on DHT therapy (group B) and 10 on placebo (group C).
Local administration of DHT was followed by the complete disappearance of gynaecomastia in 10 patients, partial regression in 19 and no change in 11 patients after 4 to 20 weeks of percutaneous DHT (125 mg twice daily). Before treatment the T + DHT/E2 ratio was significantly (P < 0.001) lower in group A 244·21 (SEM) than in groups B and C (361·21) while T, DHT and E2 concentrations were all within the normal range. During DHT treatment plasma hormone levels were measured in 26 patients from group A: DHT levels increased significantly (day 0: 1.63 ± 0.14 nmol/1; day 15: 12.8 ± 1.6 nmol/1, P < 0.001) while T and E2 levels fell significantly (T: day 0:22.6 ± 1.2 nmol/1; day 15:11.0 ± 1.5 nmol/1, /)<0.001;E2: day 0: 110.5 ± 7.1 pmol/1; day 15:86.79 ± 9.4 pmol/1, P < 0.01). The T/E2 ratio decreased from 231 ± 20 to 164 ± 27 (P < 0.05) while the T + DHT/E2 ratio increased significantly (P < 0.02) to a normal mean value (day 15: 354 + 57). Identical hormonal changes were observed in group B. Furthermore it was observed that LH plasma levels decreased (day 0: 7.8 ± 1.0 mU/ml; day 10: 4.2 ± 0.8 mU/ml, P < 0.05), while there was no significant variation of hormonal parameters in group C.
Chronic percutaneous DHT administration appears to be an efficient treatment for persistent idiopathic gynaecomastia since it caused a reduction in 29 out of 40 cases. The effectiveness seems to be due principally to systemic effects which include an increase in DHT levels and a decrease in testicular E2 and T secretion following a reduction in LH secretion.