Halotestin® (fluxymesterone)

Endogenous androgens are responsible for normal growth anddevelopment of the male sex organs and for maintenance of secondary sexcharacteristics. These effects include growth and maturation of theprostate, seminal vesicles, penis, and scrotum; development of malehair distribution, such as beard, pubic, chest, and axillary hair;laryngeal enlargement, vocal cord thickening, and alterations in bodymusculature and fat distribution. Drugs in this class also causeretention of nitrogen, sodium, potassium, and phosphorus, and decreased urinaryexcretion of calcium. Androgens have been reported to increase proteinanabolism and decrease protein catabolism. Nitrogen balance is improvedonly when there is sufficient intake of calories and protein.

Androgens are responsible for the growth spurt of adolescence andfor eventual termination of linear growth, brought about by fusion ofthe epiphyseal growth centers. In children, exogenous androgensaccelerate linear growth rates, but may cause disproportionateadvancement in bone maturation. Use over long periods may result infusion of the epiphyseal growth centers and termination of the growthprocess. Androgens have been reported to stimulate production of redblood cells by enhancing production of erythropoietic stimulationfactor.

During exogenous administration of androgens, endogenoustestosterone release is inhibited through feedback inhibition ofpituitary luteinizing hormone (LH). At large doses of exogenousandrogens, spermatogenesis may also be suppressed through feedbackinhibition of pituitary follicle stimulating hormone(FSH).

Inactivation of testosterone occurs primarily in the liver.