Principles of Biochemistry Volume 3 - A. Lehninger 1985

Selected Aspects of Human Biochemistry
Hormones
Somatotropin also influences the action of insulin

Somatotropin, or Growth Hormone, secreted by the anterior Pituitary Gland, was first identified by its ability to stimulate skeletal growth and increase body weight in young animals. A deficiency of this hormone leads to dwarfism (Fig. 25-21), whereas its excessive secretion results in gigantism or acromegaly, which is characterized by the accelerated growth of the hands, feet, and particularly the facial bones, leading to a massive lower jaw and heavy brow ridges. Somatotropin also has a profound effect on Carbohydrate METABOLISM. Administering an excess of somatotropin to animals induces pituitary diabetes, caused by the hormone's inhibitory effect on Insulin secretion. Somatotropin is a polypeptide consisting of 191 amino acid residues (molecular weight 21,000). As noted above, the secretion of this hormone is inhibited by hypothalamic Somatostatin.

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Fig. 25-21. General Tom Thumb, who apparently suffered from somatotropin deficiency, with his circus impresario P. T. Barnum.

Fig. 25-22. Hormonal Regulation of Blood glucose levels.

Figure 25-22 illustrates the complex interplay in the hormonal REGULATION OF GLUCOSE metabolism, which is influenced by Hormones from five different Endocrine glands, including the adrenal cortex (see below).