Ho

Dehydroepiandrosterone (77)

4-Androstenedione (25) Estrone (88)

4-Androstenedione (25) Estrone (88)

Testosterone (15)

Estradiol-17p (16)

Testosterone (15)

Estradiol-17p (16)

Estra-3, 16a,17p-triol (89)

Estra-3, 16a,17p-triol (89)

FIGURE 2-23 Pathway of estrogen biosynthesis. The main steps of metabolism are numbered (in circles) according to the reactions described in Figure 2-18 and Table 2-6.

drosterone sulfate (84) (DHEA sulfate), which acts as a precursor for the estriol (88) of both the placenta and the mother, is discussed in Chapters 10 and 14.

17/3-Estradiol (16) has also been found to be hydrox-ylated by brain tissue on either carbon-2 or carbon-4 to yield a family of steroids with vicinal3 phenolic hydroxyl moieties. These steroids are referred to as the catechol estrogens because of their structural similarity in the A ring to the catecholamines, epinephrine, and norepinephrine (see Chapter 11). Figure 2-24 summarizes the known pathways of metabolism for the production and breakdown of the catechol estrogens.

F. Biosynthesis of Vitamin D Metabolites

Vitamin D3 is chemically closely allied to the classical steroid hormones. Technically it is a secosteroid; that is, due to the breakage of the carbon-9, carbon-10

3 Vicinal hydroxyls are hydroxyl groups on adjacent carbons.

2. Steroid Hormones

2. Steroid Hormones

Estradiol (16)

Estradiol (16)

2-Hydroxyestradiol (92)

NAOPH, 02

NAOPH, 02

4-Hydroxyestradiol (90)

catechol o-methyltransfepase catechol o-methyltransfepase

hjco hjco'

2,3-dimethoxyestradiol (91)

Epinephrine

FIGURE 2-24 Metabolic pathways for biosynthesis of the catechol estrogens (top) and their structural similarity to the catecholamines (bottom).

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Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

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