Serum osteocalcin and other indices of bone formation: an 8-decade population study in healthy men and women.

In a study of 435 healthy men and women aged 17-97 yr, serum osteocalcin and alkaline phosphatase were measured together with 99TcMDP retention in women. In women, serum osteocalcin falls to a nadir at 35-39 yr, and the mean then rapidly rises 2-fold to a plateau from 50-75 yr. 99TcMDP retention falls to a minimum at 40-45 yr and then rises steadily with increasing age. Serum alkaline phosphatase rises in an indeterminate fashion from 20-25 yr onwards. Osteocalcin in men fell until age 60-70 yr and hardly changed thereafter, whereas serum alkaline phosphatase reached a minimum at age 30-40 yr and thereafter rose with age, as in women.