Oestradiol-17\g=b\,diethylstilboestrol (DES), dl-dihydrodibutylstilboestrol (dl-DHBS) and meso-dihydrodibutylstilboestrol (meso-DHBS) were injected intramuscularly into male Sprague-Dawley rats in a daily dose of 100 \ g=m\ g for a period of 10 days. Oestradiol-17\g=b\ and DES decreased the weight of the prostate and seminal vesicles to the same extent, whereas meso\x=req-\ DHBS was less effective. dl-DHBS was almost inactive. Only oestradiol\x=req-\ 17\g=b\ and DES caused a decrease in the weight of the testes. The adrenal glands increased in weight after administration of either oestradiol-17\g=b\, DES or meso-DHBS.Four hormones in the plasma were measured: testosterone, androstenedi\x=req-\ one, prolactin and interstitial cell-stimulating hormone (ICSH). DES decreased the plasma concentration of both ICSH and testosterone. Oestradiol-17\g=b\ and meso-DHBS administration resulted in a lowering of the plasma testosterone concentration with no effect on ICSH. Oestradiol-17\g=b\, DES and meso-DHBS markedly increased plasma prolactin concentrations. dl-DHBS appeared to have little biological effect causing only very small changes in all the parameters investigated.

Menstrual-cycle patterns of salivary progesterone concentration were obtained for 131 and 245 adolescent girls up to 4 years postmenarche living in Britain and Thailand respectively. These patterns were graded on a scale of 1 (little or no activity) to 5 (activity similar to that exhibited by the mature premenopausal woman) and the frequency of these grades within groups of girls from each centre was analysed. The major finding was that British girls exhibited a predominance of higher grades of progesterone activity when compared with their Thai counterparts (n = 2 x 58) when matched for chronological and gynaecological ages (P approximately 0.002). This was particularly so for the girls from these two matched groups in the gynaecological age range 2-4 years (P approximately 0.03). The major contribution to this significant difference between the two groups is attributed to the greater effect of chronological age on progesterone secretion in the British girls (P approximately 0.03) compared with the Thai girls (P approximately 0.29). These findings may have implications for facilitating our understanding of the reason for the differing risk of breast cancer in women in both countries.

2-Bromo-\g=a\-ergocryptine(CB154) administration to male rats produced a significant decrease in plasma prolactin levels without changing the LH and testosterone concentrations. The weights of the accessory sex tissues, testes, adrenals and kidney were unaltered by the treatment. Zinc concentration and distribution in the cell organelles of the prostatic tissue was markedly changed by CB154 treatment. No changes in the uptake of testosterone in vivo occurred in the treated animals. Prolactin did not consistently influence the prostatic adenyl cyclase activity in vitro and only at high concentrations was the testosterone uptake in vitro with cultures of prostatic tissue increased. The precise mechanism by which pituitary hormones affect the prostate is uncertain although a great deal of evidence for their influence on this gland has accumulated. Following hypophysectomy in the dog a greater prostatic atrophy occurred than after castration (Huggins 8c Rüssel 1946). A diminished prostatic response to exogenous androgen was noted in the hypophysectomized rats (Van der Laan 1953). Subsequently prolactin was reported to augment

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