Immunoreactive somatomedin B (RIA-B) in the circulation of healthy adults and patients with endocrine disorders.

ABSTRACT

PIP: The polypeptide called somatomedin B was radioimmunoassayed in serum or cerebrospinal fluid from volunteers throughout the lifespan, the daily and menstrual cycles, in oral contraceptive users, and in several patients with endocrinological disorders. This peptide, of 5000 molecular weight, is said to have insulin-like growth promoting activity, but its actual origin and function are unknown. In serum, there were no significant variations between the sexes, over the ages 20-60, in the diurnal or menstrual cycle, or by height, weight or body surface. There were significant declines after the age of 60 and 70 years in serum. The serum level in 8 women aged 20-40 taking oral contraceptives was significantly higher than that of 46 drug free women (p.001). In cerebrospinal fluid, there was a diurnal variation, a nadir at 2000 hours, but there was no decline in older individuals. Somatomedin B was significantly lower in patients with hypopituitarism and diabetes mellitus, and higher in those with hyperthyroidism and Cushing's syndrome. This is the first demonstration of somatomedin B in cerebrospinal fluid.