Steroid hormone androgen

A. Mechanism of Action Like other steroid hormones, androgens enter cells and bind to cytosolic receptors (Figure 39-2). The hormone-receptor complex enters the nucleus and modulates the expression of certain genes. 

The steroid hormones, androgens and oestrogens also are absorbed slowly, and Demole (1932) claims that their effect is diminished and delayed when they are given by the mouth. 

Steroid Hormones and Neurosteroids. Steroids (qv) can affect neuroendocrine function, stress responses, and behavioral sexual dimorphism (78,79) (see Steroids). Mineralocorticoid, glucocorticoid, androgen, estrogen, and progesterone receptors are localized in the brain and spinal cord. In addition to genomic actions, the neurosteroid can act more acutely to modulate the actions of other receptors or ion channels (80). Pregnenolone [145-13-17, ( ) dehydroepiandosterone [53-43-0] C H2 02 (319) are excitatory neurosteroids found in rat brain, independent of adrenal... 

Steroid hormones can be subdivided into sex hormones (androgens, estrogens, and progestins) and corticosteroids (glucocorticoids and mineralocorticoids). 

Sex steroid receptors are members of the steroid hormone receptor (SHR) family that ligand-dependently regulate functions of the sexual organs. Sex steroid receptors are the androgen receptor [1] (AR), the estrogen receptor a [2] and (3 [3] (ERa, ER 3), and the progesterone receptor [4] (PR). 

Pyridoxal phosphate is a coenzyme for many enzymes involved in amino acid metabolism, especially in transamination and decarboxylation. It is also the cofactor of glycogen phosphorylase, where the phosphate group is catalytically important. In addition, vitamin Bg is important in steroid hormone action where it removes the hormone-receptor complex from DNA binding, terminating the action of the hormones. In vitamin Bg deficiency, this results in increased sensitivity to the actions of low concentrations of estrogens, androgens, cortisol, and vitamin D. 

Steroid hormones are divided into six classes, based on physiological effects estrogens, androgens, progestins, glucocorticoids, mineralocorticoids and vitamin D 847... 

Fig. 1.1. General mechanism of action of steroid hormones. Steroid hormones cross through the plasmatic membrane without apparent difficulty favored by gradient. Some, which can be considered prohormones, are metabolized and transformed into more active products. This is the case with testosterone, which becomes dihydrotestosterone (DHT) in the target tissues of androgens, through the 5-alfa-reductase enzyme. The hormone binds to the receptor, a soluble protein of the cellular cytosol that, in the absence of hormone, is found associated with other proteins (hsp90 and others) that maintain the receptor in an inactive state. The hormone-receptor bond causes the other proteins to separate and a homodimer to be formed. The homodimer is the activated form of the receptor since it is capable of recognizing the genes that depend on that steroid hormone as well as of activating its expression, which leads to the synthesis of specific proteins...

Steroid hormones Estrogens Androgens Gestagens Corticosteroids... 

The interaction between the adrenal cortex of the foetus and the placenta in production of steroid hormones is complex. In outline, the placenta produces progesterone from cholesterol (which is available from the maternal blood) whereas the foetal adrenal cortex produces corticosteroids and androgens from the progesterone produced in the placenta. The placenta then converts some of these androgens into oestrogens. The interplay between the placenta and the foetal adrenal cortex is acknowledged by the use of the term foeto-placental unit to describe steroido-... 

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