We hypothesize that, with respect to non-sexual somatic and psychological parameters, males primarily thrive on oestrogens, not testosterone. The clinical impact of this sex hormone imbalance is unknown. Adverse effects from letrozole were relatively minor and included loss of libido (54%), headaches (25%), fatigue (21%), weakness (13%), loss of hair (8%) and dry mouth (8%). The ability to restore testosterone rather than replace it may change the way the aging male will pursue his health in the golden years. As expected, GH-deficient boys treated with GH and anastrozole showed a larger increase in height than their GH only-treated controls . Both groups showed similar growth velocity but bone age progressed significantly slower in the letrozole group resulting in a gain of 5.9 cm in predicted adult height. Peripheral androgen aromatization is enhanced in subjects with increased body mass index . This is extremely important and must be remembered by all readers investigating the use of aromatase inhibitors. Attempt to avoid the use of aromatase inhibitors at all costs unless absolutely necessary. As an aromatase inhibitor, it holds the ability to exert control over literally all of the potential Estrogenic side effects that anabolic steroid users attempt to avoid or eliminate. As our ability to better diagnose and recognize this complex disease process improves, clinicians will understandably seek to improve the safety and efficacy of the existing treatment modalities. As there are definite changes seen with the use of HCG, its use is tempered by the lack of large, well-designed efficacy studies. IPSS scores were not changed with exogenous testosterone or HCG preparations (35). In this study there were significant changes in the International Index of Erectile Function (IIEF-5) and Aging Male Symptom Score (AMS) but no difference between the groups. As gynecomastia in men presumably results from an imbalance between androgen and estrogen action, aromatase inhibition was tested as a treatment for gynecomastia in boys. It is well known that aromatase inhibition results in a dramatic reduction of tumor estrogen concentrations . This combination treatment effectively increased growth velocity but epiphysial maturation was slower in the letrozole-treated group, leading to a significant increase in predicted adult height 64,65. HCG was originally used for the treatment of female infertility by promoting follicular maturation and the progression of the immature oocyte. Total testosterone to total estradiol ratio at baseline, 6 and 12 weeks with clomiphene citrate and anastrozole. When it comes to subjective clinical improvement the quantitative ADAM scores showed no overall change but there was a small positive trend to improvement in both arms of treatment. It was thus hypothesized that the lack of change in clinical parameters may be the result of a decrease in estradiol with AIs. Although testosterone induces growth velocity, the estrogens aromatized from testosterone will accelerate epiphysial maturation and for that reason reduce adult height further. Boys with a mean age of 11 years at the start of the study were treated with letrozole 2.5 mg once daily or placebo for 2 years . In an earlier study a combination of spironolactone and testolactone proved effective , whereas in later studies the combination of bicalutamide and anastrozole was used 57-59. Aromatase inhibitors, therefore, may be used to lower estradiol levels and thereby slow down epiphysial maturation. Uncontrolled studies using anastrozole, testolactone or letrozole have shown some evidence for a positive effect on sperm concentration and motility 49-51. Aromatase inhibition results in a three-fold increase in levels of FSH 28,29 in eugonadal men and may potentially stimulate sperm production. Although FSH release is primarily under the control of inhibin, circulating estradiol has a substantial effect on FSH levels in men . Acting as an antagonist on these target organs, it will increase endogenous hormones such as gonadotropin-releasing hormones (GnRH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Originally an agent for female infertility and hyper estrogen states, CC exerts its effect on the hypothalamus and the pituitary gland. As awareness continues to grow for testosterone deficiency in the media as well as the health care community, a clear trend demonstrating a rise in testosterone replacement treatment is seen. This results in low testosterone and low or inappropriately low gonadotropin levels. It is important to understand how the axis operates as our treatment options target various parts of the hormone axis. The diagnosis of adult onset hypogonadism consists of clinical and biochemical deficiencies of testosterone. The most important distinction between this group of medications and testosterone replacement is that they alter endogenous testosterone production and thus can be considered restorative rather than replacement therapy.