Why It Matters
Testosterone is the primary anabolic androgen in both male and female athletes. It drives muscle protein synthesis, red blood cell production, bone density maintenance, and libido. In the context of athlete monitoring, total testosterone reflects the overall androgenic environment, while free testosterone (the unbound, biologically active fraction) is the operationally relevant measure for performance and recovery (source, source).
Testosterone interacts directly with muscle satellite cells and androgen receptors to promote hypertrophy and accelerate recovery from training stress. It also modulates mood, motivation, and competitive drive, making it relevant not just for physiology but for behavioral readiness (source).
Low Testosterone: Suppression, Overtraining, and Underfueling
Suppressed testosterone in male athletes typically signals overtraining syndrome, caloric restriction, sleep deprivation, or hypothalamic-pituitary axis dysfunction. In female athletes, low testosterone often accompanies Relative Energy Deficiency in Sport (RED-S), which disrupts the entire hormonal axis (source, source).
The testosterone-to-cortisol (T:C) ratio is a particularly sensitive marker of training stress; a falling T:C ratio over successive training weeks indicates catabolic dominance and insufficient recovery. Athletes with chronically low testosterone report decreased motivation, poor sleep quality, reduced strength, and prolonged soreness after training (source).
Other causes include zinc deficiency, vitamin D insufficiency, and elevated SHBG (which reduces the free fraction even when total testosterone appears normal). Always evaluate total testosterone alongside free testosterone and SHBG before drawing conclusions about androgenic status.
High Testosterone: Natural Variation and Exogenous Signals
Elevated testosterone in the absence of exogenous supplementation most often reflects natural variation, particularly in well-rested athletes during phases of lower training load. Post-competition spikes and testosterone elevations in response to resistance training are well-documented and physiologically expected (source).
Persistently supraphysiologic total testosterone in male athletes, especially when accompanied by elevated hematocrit, suppressed LH/FSH, and dyslipidemia, may indicate exogenous androgen use. In female athletes, elevated testosterone warrants evaluation for polycystic ovarian syndrome (PCOS) or adrenal disorders (source).
Coaching Application
Monitor testosterone trends across training blocks, not just single-point values. A 20–30% drop in total testosterone from baseline over a training cycle is a meaningful signal worth addressing through load management, nutrition, and sleep optimization. Combine testosterone with cortisol, LH, SHBG, and IGF-1 to build a complete picture of anabolic-catabolic balance and recovery capacity (source).
For female athletes, reference ranges are significantly lower (0.1–3.3 nmol/L total testosterone) and must be interpreted with cycle phase, contraceptive use, and RED-S risk in mind.
