Endocrinology--the way we were: a personal history of somatomedin.

Fifty years ago there was no practical method for measuring growth hormone (GH) activity in human plasma. In an attempt to develop such an assay, it was determined that much of the action of GH in vivo on rat cartilage was mediated by a serum factor that was first known as sulfation factor, and later as somatomedin and insulin-like growth factor. This narrative describes my experience and that of others in this important area of endocrine research.

Growth hormone axis overview--somatomedin hypothesis.

The possibility that the action of growth hormone (GH) on cartilage is mediated by a separate hormonal agent found in serum was suggested by incubation with hypophysectomized rat costal cartilage. The stability of this tissue permitted long incubations and the measurement of the uptake of 35S-sulfate provided a convenient index of growth stimulation. Under the conditions arbitrarily selected, normal rat serum, but not serum from hypophysectomized rats, induced a great stimulation of 35S uptake.