Rates of Production of Metabolites of Testosterone
In normal men, the production rates of testosterone and the adrenal androgen, androstenedione, average some 5 and 3mg/d, respectively, and the production rates of oestrone and oestradiol average approximately 66 and 45┬╡g/d, respectively (Fig. 11.9a). All of the oestrone is formed from circulating precursors; thirty-five per cent of oestradiol is derived from circulating testosterone, fifty per cent from oestrone, and fifteen per cent is secreted by the testes. When gonadotrophin levels are elevated, oestradiol secretion by the testis increases .
