Human Growth Hormone is an injectable hormone that can be administered subcutaneously or intramuscularly. When injected subcutaneously, HGH carries a bioavailability of approximately seventy-five percent. When injected intramuscularly, HGH carries a bioavailability of approximately sixty-three percent. The mode of administration will also affect the half-life of the Somatropin hormone. When injected subcutaneously, it will carry a half-life of approximately hours. When injected intramuscularly, it will carry a half-life of approximately hours. While this is a rather short half-life regardless of the mode of administration, keep in mind the total effects far outlast these numbers due to the pronounced and significant increases in IGF-1 production that stretch far past the twenty-four hour mark.
This volume is an outgrowth of a symposium held at the University of Michigan, Ann Arbor, Michigan, October 27-29, 1975. This symposium was organized to bring together basic scientists and clinicians for the purpose of exchanging new ideas and the latest information in the area of Steroid Hormone Action and Cancer. The design of the symposium included both formal plenary sessions and informal roundtable discussion groups, the chapters of this volume being drawn primarily from these proceedings. During the last quarter of a century considerable progress has been made toward understanding the molecular mechanisms in volved in steroid hormone action. It now appears that the mechan sim of action of the four major classes of steroid hormones is qualitatively similar. Research during the past decade has demonstrated steroid hormone receptors in a variety of normal and neoplastic tissues. Receptor-containing neoplasms have been shown to be hormone-dependent and undergo regression when treated with hormone antagonists. Natural and synthetic steroids also have been employed for many years to successfully treat various types of cancer, for example: estrogens, androgens and progestagens for breast cancer; estrogens and progestagens for prostatic carcinoma; progestagens for endometrial carcinoma; and corticoids for leu kemias. All of these neoplasms have now been found to possess receptors for the steroids empirically used in their treatment.
Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.