[Changes in steroid enzyme activities with age in human ovary]

Area of Science:

• Reproductive Endocrinology
• Steroid Biochemistry
• Gerontology

Background:

• Sex hormone secretion naturally decreases with advancing age.
• Ovarian function and steroid metabolism undergo significant changes throughout a woman's lifespan.

Purpose of the Study:

• To investigate age-related alterations in key steroidogenic enzyme activities within human ovarian tissues.
• To elucidate the specific changes in 17 alpha-hydroxylase (17hy), 20 alpha(beta)-hydroxy steroid dehydrogenase (20-HSD), C17-20 lyase, 17 beta-hydroxy steroid dehydrogenase (17 beta-HSD), and aromatase activities.

Main Methods:

• Ovarian tissues were obtained from women aged 30-81 years.
• Enzyme activities were quantified by measuring the conversion of radiolabeled progesterone, 17 alpha-hydroxy progesterone, and androstenedione.
• Specific enzyme assays were performed to assess 17hy, 20-HSD, C17-20 lyase, 17 beta-HSD, and aromatase function.

Main Results:

• A significant reduction in C17-20 lyase and 17hy activities was observed in premenopausal women compared to reproductive women.
• Aromatase, 17 beta-HSD, and 20-HSD activities showed no significant change in the premenopausal stage.
• Postmenopausal ovaries exhibited decreased 17hy activity, reduced aromatase activity, and unchanged 17 beta-HSD and 20-HSD activities.
• The formation of 17 alpha, 20 beta-OH-P4 from 17P4 was demonstrated, indicating 20 beta-HSD activity in postmenopausal ovaries.

Conclusions:

• Ovarian steroid enzyme activity changes with age are primarily characterized by a marked decrease in C17-20 lyase and 17hy.
• 17 beta-HSD and 20-HSD activities appear to be well-preserved throughout aging and menopause.
• Aromatase activity declines specifically in the menopausal stage, contributing to altered steroid metabolism.