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A,0,T,P AAA A Pregnenolone--Progesterone-DOC -Corticosterone -180H-Corticosterone-»-Aldosterone

j A,O.T,P | A A 170H-Pregnenolone ——170H-Progesterone-11-Deoxycortiso!-Cortisol f © I © ©

Dehydroepiandrosterone-Androstenedione-Testosterone-Estradiol

FIGURE 2-18 Principal pathways of human steroid hormone synthesis. The details of the enzyme reactions (circled numbers) are summarized in

Table 2-6. Reactions (2), ©, and (8) are found universally in the adrenals, ovary, testes, and placenta. Reactions © and @ are found principally in the testes and ovaries. Reactions (Jl) —> (B) describe the pathway of production from cholesterol of the prohormone vitamin D and its hormonal metabolite products la,25(OH)2D3 and 24,25(OH)2D3. Reaction P450c25 present in the mitochondrial and /or endoplasmic reticulum of the liver. Reactions @ and P450cla and P450c24 present in the mitochondria of the kidney proximal tubule. Tissue codes: A, adrenals; O, ovaries; T, testes; P, placenta; S, skin; L, liver; K, kidney; DHEA, dehydroepiandrosterone (77). [Modified from Miller, W. L. (1988). Molecular biology of steroid hormone biosynthesis. Endocr. Rev. 9, 295-318.]

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