Early menarche is a risk factor for breast cancer. In a longitudinal manner, we have investigated the endocrine features of girls with early menarche. This study extends our investigations to the third decade of life in a cohort of girls followed up for 13 years. The group studied comprised 44 women, 20-31 years of age. Eleven women had had their menarche before 12.0 years, 14 women at 12.0-12.9 years and 19 women at 13.0 years or more. The women who had had early menarche had higher serum oestradiol concentrations during the follicular phase of the menstrual cycle than the women who had had their menarche later. The serum oestradiol concentrations increased rapidly at the beginning of cycle in these "early menarche" women. If there is a threshold which serum oestradiol concentrations must exceed to increase the risk of breast cancer, then these women have more days at risk than other women. In addition, the serum SHBG (sex-hormone-binding globulin) concentration was about 30% lower in the follicular-phase specimens of the women who had had their menarche before 12.0 years compared with those who had had their menarche at 13.0 years. Our data therefore indicate that women with early menarche are subject to a high degree of oestrogen stimulation at least until approximately 30 years of age. Our findings may have important consequences for the design of intervention programs for breast cancer prevention.

Endocrine responses in seven power athletes were investigated during a 12 week strength training period, when the athletes were taking high doses of androgenic-anabolic steroids, and during the 13 weeks following drug withdrawal. During the use of steroids significant decreases (P less than 0.05 to 0.001) in the serum concentrations of thyroid stimulating hormone, thyroxine, triidothyronine, free thyroxine, and thyroid hormone-binding globulin (TBG) were found, whereas the value of triidothyronine uptake increased (P less than 0.001). In relation to the changes in the thyroid function parameters measured, we suggest that the primary target of androgen action was TBG biosynthesis. In five of the seven subjects, serum concentrations of growth hormone increased at some point of the study 5 to 60-fold. Because of the use of exogenous testosterone, serum testosterone concentration tended to increase. This increase was associated with a corresponding increase (P less than 0.001) in serum estradiol. Furthermore, there were major decreases in serum LH (P less than 0.01) and FSH (P less than 0.01) concentrations, and testicular testosterone production was therefore decreased. This was characterized by a very low serum testosterone concentration (5.1 +/- 1.8 nmol/l) 4 weeks following drug withdrawal. Cessation of drug use resulted in return of all the variables measured to the initial values, except for serum testosterone, which was at a low level (14.6 +/- 8.8 nmol/l) 9 weeks after drug withdrawal, indicating prolonged impairment of testicular endocrine function. No consistent changes were found in the eight control athletes.

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