17 beta-hydroxysteroid dehydrogenase activity in leiomyoma and myometrium and its relationship to concentrations of oestrone, oestradiol and progesterone throughout the menstrual cycle.

The activity of the enzyme 17 beta-hydroxysteroid dehydrogenase (17 beta-OHSD) and concentrations of oestrone (E1), oestradiol (E2) and progesterone have been measured in leiomyoma and myometrium obtained at different stages of the menstrual cycle. Apart from conversion of E2 to E1 in the proliferative phase, no significant difference in enzyme activity was noted between normal and tumour tissue. However, interconversion in both tissues was shown to be higher in the secretory than the proliferative phase of the menstrual cycle. E1 concentrations were significantly higher (P less than 0.01) in leiomyoma than in myometrium, obtained during the proliferative phase. Concentrations of both oestrogens, in some tumour and normal tissues, were higher in the proliferative than the secretory phase. Secretory phase tissues contained higher concentrations of progesterone than those obtained in the proliferative phase of the menstrual cycle. Considerable differences in both enzyme activity and steroid concentrations were noted in different areas of the same tumour.