1. Plasma alkaline phosphatase activity and urine hydroxyproline excretion were measured in age-matched premenopausal and postmenopausal women.
2. Both measurements were found to be significantly higher in postmenopausal women.
3. It is proposed that the rise in the plasma alkaline phosphatase, like that in the hydroxyproline excretion, may reflect the onset of bone loss that occurs after the menopause.