Why it is done this way
A diagnosis made on a full panel, then monitored
A single total testosterone drawn in the afternoon tells you very little.
Total and free testosterone, SHBG, LH, FSH, estradiol and prolactin, alongside thyroid and metabolic markers, is what separates a genuine deficiency from a number near the bottom of a wide reference range.
Once treatment starts, hematocrit, PSA and estradiol are tracked on a schedule. Replacement without monitoring is not therapy.