Tag: endocrine system and chemical co-ordination

The chief function of STH (GH) is to promote synthesis and secretion of small protein hormone called insulin like growth factors (IGFs).

The chromatin cells of adrenal medulla synthesize two hormones adrenaline or epinephrine (80%) and noradrenaline or norepinephrine (20%).

Hormones are also grouped into three general structures as follows:

1. Steroid hormones are fat-soluble molecules made from cholesterol. Among these are the three major sex hormones groups: estrogens, androgens and progesterones. Males and females make all three, just in different amounts. Steroids pass into a cell's nucleus, bind to specific receptors and genes and trigger the cell to make proteins.
2. Amino acid derivatives, such as epinephrine, are water-soluble molecules derived from amino acids (the building blocks of protein). These hormones are stored in endocrine cells until needed. They act by binding to protein receptors on the outside surface of the cell. The binding alerts a second messenger molecule inside the cell that activates enzymes and other cellular proteins or influences gene expression.
3. Insulin, growth hormone, prolactin and other water-soluble polypeptide hormones consist of long chains of amino acids, from several to 200 amino acids long. They are stored in endocrine cells until needed to regulate such processes as metabolism, lactation, growth and reproduction.