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The activity of 17 beta-hydroxysteroid dehydrogenase (17 beta HSD) was measured in human breast tumours and in normal breast tissue from premenopausal, perimenopausal and postmenopausal women. Enzyme activity was higher in tumour tissue than in normal tissue from the same breast and under the conditions of the assay the oxidation of oestradiol was higher than the reduction of oestrone. The physiological status of the women in the study did not relate to the activity of the enzyme in either normal or tumour tissue although fibroadenomas had less activity than adenocarcinomas. In postmenopausal women tumour tissue oestrogens were 2-3 fold higher than in normal tissue from the same breast. Furthermore, tumour tissue concentrations of oestradiol tended to be higher than those of oestrone although in normal tissue the two oestrogens were present in similar concentrations. In plasma from the same women oestrone was the predominant oestrogen. There appears to be no direct relationship between 17 beta HSD activity and oestrogen concentrations but the enzyme may play a part in determining the balance between oestrone and oestradiol according to substrate and cofactor availability.

The purpose of this study was to investigate the effect of calorie restriction on serum concentrations of sex hormone binding globulin (SHBG) in women with normal or polycystic ovaries (PCO) and to examine the possible role of insulin and insulin-like growth factor-I (IGF-I) in mediating changes in SHBG levels. Six normal subjects with mean (SD) body mass index (BMI) 25.5 (2.2) and five subjects with PCO (BMI 36.1 (3.7)) were studied before and after 2 or (PCO only) 4 weeks of a very low calorie diet (330 kcal/day; Cambridge Diet). In both normal women and patients with PCO there was a twofold increase in SHBG concentrations after 2 weeks and this was sustained in the PCO subjects for a further 2 weeks. The rise in SHBG was accompanied by a fall in free testosterone concentrations. There were parallel changes in serum insulin and IGF-I concentrations which decreased during the diet and there were significant negative correlations of SHBG with insulin in both normal subjects (r = -0.62) and women with PCO (r = -0.60). In addition, serum concentrations of an insulin-dependent small molecular weight (34 kDa) binding protein for IGF-I (IGF-BPI) increased significantly during dieting in both groups and were negatively correlated with serum insulin (controls, r = -0.56; PCO, r = -0.68) and positively correlated with serum SHBG levels (controls, r = 0.69; PCO, r = 0.63). In summary, these data indicate that in both normal subjects and those subjects with PCO, calorie restriction results in a highly significant increase in SHBG concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)