Sex hormones (total/free T, SHBG, E2, LH/FSH, DHEA-S)
Diagnostics · HPG axis
Tier A
What this is
Measure at 7-10 AM fasted (diurnal variation of 30-40% over the day). 'Free' vs 'bioavailable' vs 'calculated free' testosterone controversy — calculated free (from total + SHBG + albumin) is usually most reliable; direct 'free T' immunoassays unreliable. Repeat low values before diagnosing hypogonadism per Endocrine Society guidelines.
Mechanism
Total testosterone = total; free testosterone (or calculated from SHBG) = bioactive; SHBG rises with age, estrogen, thyroid; LH/FSH distinguishes primary vs secondary hypogonadism; estradiol in men matters for TRT management
Dose & route
Baseline + periodic; AM collection essential (diurnal variation)
Citations
- https://pubmed.ncbi.nlm.nih.gov/29562364/
- https://pubmed.ncbi.nlm.nih.gov/29946746/
- https://pmc.ncbi.nlm.nih.gov/articles/PMC8040526/
Links go to the source. If a link is dead or you want something re-checked, let me know.
This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.