Testosterone metabolism: what changes your levels and why
Testosterone metabolism is how your body converts, activates, and gets rid of testosterone. That process decides how much active hormone reaches tissues, and it explains why two people with the same blood number can feel very different. Knowing the main steps and common drug or lifestyle effects helps you make smarter choices and avoid surprises.
Key pathways and enzymes
Three things matter most: conversion enzymes, binding proteins, and liver clearance.
First, 5-alpha reductase turns testosterone into dihydrotestosterone (DHT), which is stronger at some receptors. Drugs like finasteride block this step and lower DHT without always changing total testosterone. Second, aromatase converts testosterone into estradiol. Fat tissue has aromatase, so more body fat often means more conversion to estrogen. Third, the liver adds chemical tags (glucuronidation via UGT enzymes and some CYP activity) so testosterone and its breakdown products can be cleared in urine and bile. Genetic differences in UGT enzymes (for example UGT2B17) change how fast people clear testosterone and can affect lab tests.
Sex hormone–binding globulin (SHBG) also matters. SHBG grabs testosterone in the blood and makes it inactive. If SHBG goes up, free testosterone drops even if total testosterone looks OK. Thyroid status, estrogen levels, age, and some drugs change SHBG.
What alters metabolism — drugs, health, and habits
Medications can shift the balance. 5-alpha reductase inhibitors reduce DHT. Certain diuretics like spironolactone have anti-androgen effects. Some antibiotics, antifungals, and other meds change liver enzymes and can speed up or slow steroid clearance — that changes measured levels and effects. Enzyme inducers (rifampin, some seizure meds) can lower hormones faster; strong inhibitors may slow clearance. Always check with a clinician before combining drugs.
Body weight, alcohol, liver disease, sleep, illness, and inflammation also change metabolism. Losing excess fat often reduces aromatase activity and can raise free testosterone. Heavy alcohol use and liver disease blunt hormone production and clearance in complex ways. Good sleep and resistance training tend to support healthy testosterone action.
For anyone tracking hormones: don’t rely on one number. Ask for total testosterone, free testosterone (or calculated free), SHBG, and estradiol when relevant. If you’re on drugs that affect hormones or liver enzymes, tell your doctor so they interpret labs correctly.
Practical steps: maintain a healthy weight, lift weights, sleep well, limit alcohol, review current meds with your clinician, and avoid unregulated hormone supplements. If you suspect a drug interaction or weird lab results, get a focused hormone panel rather than guessing.
Understanding testosterone metabolism helps you ask better questions at the clinic and take actions that make a real difference. If you have specific meds or symptoms in mind, bring that list to your healthcare provider — it makes the next steps much simpler.
