Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes. 
We have also noted that 24-hour urinary estrogens can be a sensitive monitor of liver detoxification capability. Elevated urinary estrogens in normally-cycling women may indicate a history of exposure to liver stresses such as excessive environmental organic chemicals. Interventions intended to improve liver function result in a gradual normalization of the abnormal estrogen levels. Thus, measurement of urinary estrogens can give insight into other aspects of physiology. This phenomenon is also noted in peri- or post-menopausal women who have previously taken Premarin, and have switched to triple-estrogen replacement with less-than-optimal symptom relief.
FIGURE 2. Major Pathways of Steroid Biosynthesis.
The pathways outlined here are common to the adrenals, the gonads and, to some extent, to the fetoplacental unit. The first committed step is the conversion of cholesterol to pregnenolone, catalysed by the P-450scc enzyme, which is under pituitary hormone control (ACTH or LH depending on the tissue). Cholesterol side-chain removal is blocked specifically by aminoglutethimide , a steroid biosynthesis inhibitor. From pregnenolone, steroid biosynthesis can proceed either through the so-called "delta-5" pathway (17α-hydroxypregnenolone, dehydroepiandrosterone, testosterone), or through the "delta-4" pathway (progesterone onwards). Progesterone is the starting point for mineralocorticoid synthesis, whereas glucocorticoids are derived from its metabolite, 17α-hydroxyprogesterone. Estrogens are formed from androgens (androstenedione and/or testosterone). Most reactions are irreversible (as denoted by a single arrow). Reversible reactions (double arrows) depend on cofactor availability (. the NADP/NADPH ratio). [Abbreviations used here for the various enzymes are listed in the figure].