Diagnosis and monitoring are two different lists, and conflating them is why panels are simultaneously bloated and incomplete.
For diagnosis
Fasting morning total testosterone — twice. The recommended initial test, using an accurate and reliable assay, with the diagnosis confirmed by repeating the fasting morning measurement.[1] Not once. Not in the afternoon. Not after breakfast.
Free testosterone — when indicated. Required when total sits near the lower limit of normal, or when a condition altering SHBG is present, obtained by equilibrium dialysis or an accurate formula.[1] SHBG-altering conditions are common: age, obesity, thyroid disease, liver disease, diabetes, and several medications.
Tests to establish the cause. The guideline recommends additional diagnostic evaluation to ascertain the cause of a confirmed deficiency,[1] which is where pituitary hormones earn their place — distinguishing a testicular problem from a signalling one.
Symptoms, documented. Not a lab test, but half the diagnosis. Hypogonadism is diagnosed only in men with symptoms and unequivocally, consistently low concentrations.[1]
Why free testosterone and SHBG matter more with age
Because they diverge. The European Male Ageing Study measured total testosterone falling about 0.4% a year and free testosterone about 1.3% — roughly three times faster.[2]
A total-only panel in an older man is measuring the slowest-moving number available. The mechanism is in SHBG and the binding problem.
For monitoring
A different list, and shorter than most people expect. The guideline's standardised plan for the first year:[1]
- Symptoms
- Adverse effects
- Compliance — not a blood test
- Serum testosterone — against a mid-normal target
- Hematocrit
- Prostate cancer risk assessment
Hematocrit is there because erythrocytosis is the most common side effect of testosterone therapy, with published guidance to decrease or discontinue above 54%.[4] Its timing is not arbitrary either: effects on erythropoiesis become evident at three months and peak at nine to twelve.[5] That is why the first panel falls where it does — see the 3-month panel.
What is usually missing, and what is usually surplus
Missing: the confirmation draw, free testosterone and SHBG when indicated, and any attempt at the cause.
Surplus: breadth. A wide hormone panel with no confirmation draw and no free testosterone is more tests and less information.
Frequently asked questions
Do I need to fast? Yes, for the diagnostic measurements.[1]
Why twice? Testosterone varies day to day; the guideline recommends confirming by repeating the morning fasting measurement.[1]
When should monitoring bloods be drawn? Relative to your dosing schedule, as directed — otherwise the result is uninterpretable.
Is a home kit adequate? The requirement is an accurate and reliable assay.[1] Ask which assay runs the sample and whether it returns a fasting morning measurement your clinician will act on.
Next in this series
The tests are one half. What competent treatment looks like around them is the other.
Continue with what good TRT actually looks like.
References
5 sources
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744. doi:10.1210/jc.2018-00229 · PMID 29562364
- Wu FC, Tajar A, Pye SR, et al. Hypothalamic-pituitary-testicular axis disruptions in older men are differentially linked to age and modifiable risk factors: the European Male Aging Study. J Clin Endocrinol Metab. 2008;93(7):2737–2745. doi:10.1210/jc.2007-1972 · PMID 18270261
- Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999;84(10):3666–3672. doi:10.1210/jcem.84.10.6079 · PMID 10523012
- Agrawal P, Singh SM, Kohn T. Management of Erythrocytosis in Men Receiving Testosterone Therapy: Clinical Consultation Guide. Eur Urol Focus. 2023;9(1):20–21. doi:10.1016/j.euf.2022.10.008 · PMID 36335038
- Saad F, Aversa A, Isidori AM, et al. Onset of effects of testosterone treatment and time span until maximum effects are achieved. Eur J Endocrinol. 2011;165(5):675–685. doi:10.1530/EJE-11-0221 · PMID 21753068