TWENTY‐FOUR HOUR PROFILES OF CIRCULATING ANDROGENS AND OESTROGENS IN MALE PUBERTY WITH AND WITHOUT GYNAECOMASTIA

SUMMARY The possible mechanisms involved in the development of transient gynaecomastia during male puberty have been investigated by studying 24 h profiles of circulating androstenedione (Ao) and testosterone (T) and their oestrogen pairs oestrone (E1) and oestradiol (E2), in eight boys with simple delayed puberty, eleven boys with pubertal gynaecomastia (three of whom were re‐tested after its spontaneous resolution), and two normal adult men. No differences were observed between the 24 h T and Ao profiles of pubertal boys with or without gynaecomastia; we confirmed that the initial T rise was nocturnal, associated with sleep. Late in puberty daytime T levels also rise. A small rise in 24 h Ao was seen, but this was not closely related to the stage of puberty. The major new finding was that E2 and to a lesser extent E1 levels are high relative to T for prolonged periods of the afternoon and evening (when T levels are lowest) in male puberty. A frequent finding, seen only in boys with gynaecomastia and one who later developed it, was of elevated and markedly fluctuating levels of plasma E2, and an absolute increase in the area under the 24 h E2 profile and between the E2 and T profiles. These fell towards normal in three boys who were re‐tested after resolution of gynaecomastia. In a minority of subjects T and E2 were quite closely correlated, suggesting that in them rapid aromatization of T was occurring within or outside the testis. We conclude that normal male puberty is associated with relative oestrogen dominance particularly in the daytime. In boys with gynaecomastia there is in addition often an absolute elevation of E2 with or without E1, while 24 h T levels are submaximal. Normal men probably require sustained adult circulating T levels to prevent their oestrogens from stimulating breast development.