Testosterone is bioactivated into a more potent androgen in tissues expressing enzymes of the 5α-reductase family. DHT can be subsequently inactivated to 3α-androstanediol (3α-diol) by 3α-hydroxysteroid-dehydrogenase (3αHSD). After crossing the plasma membrane, AAS can undergo biotransformation or bind to their cognate receptor, the androgen receptor (AR; see Figure 3). Examples of the estimated distribution of testosterone bound to binding proteins at physiological concentrations (A) and supraphysiological concentrations (B). Thus, increasing dosages of testosterone result in a larger fraction of albumin-bound testosterone relative to the SHBG-bound fraction (see Figure 2). It is also a potent teratogen in women and therefore carries a high risk of birth defects when used during pregnancy or in the few weeks before conception. The usual treatment in clinical practice, such as benzoylperoxide or topical retinoids, is much less often used by AAS users, possibly because they favor an oral agent that is usually very effective and easy to acquire on the black market. This includes use of the oral prescription drug isotretinoin by a small percentage of users (65, 67). There is no evidence that steroid dependence develops from therapeutic use of AAS to treat medical disorders, but instances of AAS dependence have been reported among weightlifters and bodybuilders who chronically administered supraphysiologic doses. High concentrations of AAS, comparable to those likely sustained by many recreational AAS users, produce apoptotic effects on neurons,citation needed raising the specter of possibly irreversible neurotoxicity. Kidney tests revealed that nine of the ten steroid users developed a condition called focal segmental glomerulosclerosis, a type of scarring within the kidneys. Other side-effects can include alterations in the structure of the heart, such as enlargement and thickening of the left ventricle, which impairs its contraction and relaxation, and therefore reducing ejected blood volume. Although, of course, the AAS user will not necessarily disclose his use of AAS or present with side effects caused by it. With an estimated global lifetime prevalence rate of 3.3% (6.4% for males and 1.6% for females) (2), virtually every practising physician will provide care for an AAS user at some point in their career. Chemical structure of the steroid nucleus consisting of three cyclohexane rings (A–C) and one cyclopentane ring (D). Besides this valid medical use, AAS are widely used – or rather, abused – for their muscle-building and strength-increasing properties in dosages far exceeding those used therapeutically. With physiological SHBG levels in the 10–56 nmol/L range, it is clear that supraphysiological dosages of testosterone saturate its binding capacity. SHBG is present in the bloodstream as a homodimer, with each monomer having one steroid-binding site (14). However, it needs to be dosed twice daily to maintain physiological testosterone levels throughout the day. Mean body mass index (BMI) was 34.7 kg/m2, with all but one of the patients having a BMI of ≥30 kg/m2. All patients presented with proteinuria (mean 10.1 g/d; range 1.3–26.3 g/d) and all but one presented with elevated serum creatinine levels (mean 265.3 μmol/L (3.0 mg/dL); range 115.0–689.7 μmol/L (1.3–7.8 mg/dL)). If the increase indeed is causal, it remains to be determined whether this reflects a true decrease in GFR or whether AAS affect serum cystatin C concentrations by other means. Unfortunately, because of its cross-sectional setup, this study does not allow to infer causality. This allows the cell to regulate the rate of production and prevent an infinite loop, also known as a futile cycle, from forming with catabolism. Photosynthetic carbohydrate synthesis in plants and certain bacteria is an anabolic process that produces glucose, cellulose, starch, lipids, and proteins from CO2. Endocrinologists have traditionally classified hormones as anabolic or catabolic, depending on which part of metabolism they stimulate. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. While this might indicate a true difference compared with testosterone, it might also be attributed to the relatively low dosages used and small samples sizes that make the research liable to type II statistical errors (a ‘false negative’). Similar changes are seen in men receiving supraphysiological dosages (200–600 mg weekly) of testosterone enanthate (15, 37, 118, 119), although not all trials show a statistically significant decrease (34, 120, 121). While not seen in every clinical trial, treatment of hypogonadal men with testosterone therapy reduces circulating HDL-cholesterol (117). Dyslipidemia, an imbalance in these lipoproteins, is recognized as an important risk factor for CVD, and treatment thereof forms one of the cornerstones of primary and secondary CVD prevention. The collective increase in these serum markers should thus be interpreted as a sign of liver damage, even in the presence of concomitant muscular exercise. The HAARLEM study also found no (sub)acute clinical signs of liver damage despite 67% of subjects reporting the use of oral AAS (39). Anabolic Agents Compounds that interact with ANDROGEN RECEPTORS in target tissues to bring about the effects similar to those of TESTOSTERONE. C1-inhibitor is a protease that inhibits the complement system (part of the innate immune system), a biochemical chain of reactions which assists the body in removing pathogens from the body. Despite prolonged survival, Anabol-treated animals usually showed the histological findings of acute and chronic renal rejection. Anabol has been observed to antagonize several pharmacodynamic effects of serotonin in laboratory animals, including bronchoconstriction and vasodepression, and has demonstrated similar efficacy in antagonizing histamine-mediated effects. Although they effectively promote the primary goal of increasing muscle strength or size, their use is not without risks. Thus, in contrast with dysphonia and hirsutism, there appears to be a higher threshold of androgenic action required for this side effect to occur.
