The following is an excerpt from Knowledge and Nonsense by Jamie Hale (2007).

Testosterone (TST) is synthesized and secreted from the leydig cells of the testes via the hypothalamic-pituitary-gonadal (HPG) axis. A small amount is also derived from the ovaries and adrenals and from the conversion of other androgens. It decreases protein degradation and increases protein synthesis, and most evidence concludes that it has a significant effect upon muscle tissue.

TST may contribute to protein accretion by stimulating the release of other anabolic hormones. It is derived from cholesterol and isn’t freely soluble in plasma. The majority of TST is bound to albumin (~38 percent) and the sex hormone-binding globulin (SHBG) (~55–60 percent) with the remaining amount circulating freely or unbound (~2–5 percent). Unbound TST represents the biologically active fraction available to the tissues, although TST that is weakly bound to albumin may become active through its rapid dissociation from albumin. So the pool of free and albumin-bound TST has often been termed the “bioavailable” steroid.

Program design

Kraemer and colleagues compared the hormonal response of eight exercises performed with either a five repetition max (RM) load for 3–5 sets per exercise and three minutes of rest between sets or a ten RM load (three sets per exercise) with one-minute rest periods. The total TST response to the hypertrophy scheme was much greater than that reported following the neuronal scheme. These results could have been due to more total work with the hypertrophy scheme. (This is speculation though because I haven’t seen the exact loads used in the study.) Hakkinen and Pakarinen reported an increase in total TST and free TST to a hypertrophy squat session (ten sets times ten repetitions or ten RM). However, no significant changes in total or free TST occurred after the performance of a neuronal type squat session (20 sets times one repetition or one RM).

Dynamic power training protocols have also produced significant androgen responses. For example, total and free TST increased in response to half squat lifts performed with a load of 50 percent of one RM. In general, the blood TST response to hypertrophy and dynamic power schemes are of similar magnitude with neuronal schemes producing the smallest change.

Training status

Training status (experience) appears to be an important factor regarding hormonal response to exercise. Strength trained athletes have shown greater TST (total and/or free) responses than non-athletes. In addition, greater training experience is accompanied by enhanced responses. These data indicate an enhanced sensitivity of the HPG axis (and TST secretion) to resistance exercise with resistance training experience. This adaptation would positively influence the training response, particularly if combined with a training-induced increase in resting TST.

Hormone secretion may be further sensitive to the type of training experience with a less pronounced TST response found in endurance-trained males than resistance-trained and untrained males. Lowered TST secretion among endurance athletes is not uncommon and may be explained by training-related dysfunction within the HPG axis (it probably has something to do with elevated levels of ampk in endurance athletes). Lower serum TST concentrations have been shown with 1–2 weeks of high volume weightlifting.

Bodybuilders and steroid users have shown an inhibited hormone response to resistance exercise. A 70 percent reduction in TST was observed among male bodybuilders performing a lower body workout. Another study looked at the endocrine responses among bodybuilders and powerlifters that were separated into two groups—anabolic steroid users and non-steroid users. Following an intense squat workout, no significant changes in blood TST occurred in either group.

Rozenek and colleagues reported a smaller TST response to resistance exercise among steroid lifters compared with non-steroid lifters. The response may be explained by the greater TST levels in steroid lifters and lower LH levels compared to those seen in non-steroid lifters. It is possible the TST uptake and utilization is enhanced as an adaptive response to specific training practices. The secretion of other hormones and their effects on TST levels need to be considered also.


A study performed by Chandler and colleagues examined acute hormone responses to exercise with CHO and/or PRO taken immediately after and two hours after exercise. Supplementation produced a reduction in total TST in the post-exercise period compared with a placebo. A similar response was observed over three consecutive days of exercise with CHO and PRO supplementation and in response to a mixed meal, an isocaloric beverage with a similar content, and a isocaloric CHO beverage. This type of supplementation seems to exaggerate the post-exercise decline in TST. This response could be due to an increase in hormone uptake and/or clearance. The decrease in TST observed was not associated with a decline in LH, which suggests a greater hormone clearance. The ratio between TST and SHBG remained unchanged after supplementation, which is indicative of stable free testosterone levels despite lowered TST.

Some studies have shown that dietary fat has beneficial effects on serum testosterone levels. A study by Hamalainen and colleagues examined the effects of dietary fat content and the ratio of polyunsaturated to saturated fatty acids (P/S ratio) on serum sex hormones in 30 healthy male volunteers. The customary diet of the subjects, which supplied 40 percent of energy as fat (mainly from animal sources, P/S ratio 0.15), was replaced for a six-week period by a practically isocaloric experimental diet containing significantly less fat (25 percent of energy) with a higher P/S ratio. Other environmental factors were stabilized. Serum testosterone, 4-androstenedione, and serum free (non-protein bound) testosterone decreased. The results of the study indicated that in men a decrease in dietary fat content and an increase in the degree of unsaturated fatty acids reduced the serum concentrations of androstenedione, testosterone, and free testosterone.

A study by Raben and colleagues investigated serum sex hormones and endurance performance after a lacto-ovo vegetarian diet and a mixed diet. The lacto-ovo diet resulted in lower total TST levels compared with the mixed diet. After six weeks on the diets, the total TST was significantly lower on the lacto-ovo diet than on the mixed diet during exercise. Serum free testosterone, however, did not differ significantly during the six-week dietary intervention periods. There was no significant difference in endurance performance between the groups.