Steroid hormones classification

The area of nonsteroidal antiestrogens along with other classes of nonsteroidal antagonists of sex-steroid hormone action has been reviewed to 1986, and these compounds have been grouped by chemical stmcture as a basis of classification rather than any biochemical or biological test system utilized to assess antagonist activity (46). 

Ultraviolet light causes a chemical change in dihydrocholesterol to produce cholecalciferol, a precursor of vitamin D. The latter conforms better to the definition of a steroid hormone than a vitamin. Indeed, the classification of vitamin D as a vitamin is an historical accident. The precursor is released from the skin and is further modified in the liver and kidney to form dihydroxycholecalciferol, which is the active form of the hormone (see Chapter 15 for the reactions). It increases calcium absorption from the... 

Proteohormones, steroid hormones and peptide hormones may be differentiated on the basis of their chemical structure. Hormones may be classified as neurosecretory (e. g. hypothalamus), glandular (endocrine glands) or aglandular according to their source tissue. Aglandular hormones are also known as tissue hormones they are synthesized in special cells located in specific organs. Hormones may be differentiated according to their transport characteristics into unbound hormones and hormones which are coupled to a carrier protein. A further classification is based on their principal functions, (s. tab. 3.9)... 

Vertebrate hormones hormones of vertebrate animals. On the basis of studies on the phylogenetic relationships of certain proteins, proteohormones and peptide hormones, the separate classification of V.h and Invertebrate hormones (see) appears to be justified. Chemically, V.h. are a heterogeneous group, which can be subdivided into Steroid hormones (see), hormones derived from amino acids (see Thyroxin, Adrenalin, Melatonin), Peptide hormones (see), Proteohormones (see), and hormones derived from fatty acids (see Prostaglandins). There is, however, no fundamental difference between V.h. and invertebrate hormones, with respect to types of chemical structure, or biochemical mode of action. 

Classification of Hormones. Depending upon their chemical constitutions and their patterns of biosynthesis, three groups of hormones can be distinguished (1) Steroid hormones, (2) Amino acid-derived hormones, and (3) Peptide and protein hormones. Table XVIII gives a survey of known hormones and their effects. 

Classification. Classification becomes a bizarre problem by reason of the (a) overlapping uses to which these substances are put. and (b) the multiple purposes for which the hormones or synthetic substances are used. Indeed, the steroids may be classified by structure that however would be uninformative to the student as to their u.se. Classification by origin, as adrenal, would also be unsuitable because, for example, a number of the adrenal corticosteroids are not found in the adrenal cortex at all. but merely resemble the natural hormones found in the adrenal cortex. 

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