| name | icsm-testosterone-threshold-loh |
| description | This skill applies a total testosterone threshold of less than 12 nmol/L (3.5 ng/mL) to diagnose late-onset hypogonadism. It is triggered when a clinician evaluates a testosterone result and questions whether the level is low enough to diagnose hypogonadism or what cutoff defines low T. |
Apply testosterone threshold for late-onset hypogonadism diagnosis
STEP 1 — Gather Information
Obtain a morning (07:00–11:00) fasting total testosterone level using a reliable assay and assess for symptoms suggestive of LOH such as low libido, decreased morning erections, or erectile dysfunction.
STEP 2 — Rule In / Rule Out
Is the total testosterone level <12 nmol/L (3.5 ng/mL)? If yes, proceed to step 3; if no, consider LOH unlikely based on this threshold and evaluate other causes of symptoms.
STEP 3 — Classify or Stratify
Repeat total testosterone measurement on a separate occasion; if the second result is also <12 nmol/L, confirm biochemical LOH; if not, treat as transient low and reconsider diagnosis or repeat testing.
STEP 4 — Decide
If confirmed low testosterone (<12 nmol/L on two occasions) and LOH‑related symptoms are present, diagnose late‑onset hypogonadism and discuss testosterone therapy after reviewing risks and benefits; if symptoms are absent, generally refrain from initiating therapy based solely on low T.
Clinical Guardrails / Mimics / Pitfalls
Do not diagnose LOH on a single low testosterone; avoid testing during acute illness; do not ignore SHBG and albumin in men with clear dysmetabolic conditions when calculating free testosterone; do not start testosterone therapy without confirming low T on two separate occasions; do not treat asymptomatic men solely on the basis of a low total testosterone level.
Concrete Clinical Example
A 58‑year‑old man presents with decreased libido and fewer morning erections. His morning total testosterone is 10.8 nmol/L. A repeat test one week later shows 11.2 nmol/L. Both values are below 12 nmol/L, and he reports relevant symptoms, leading to a diagnosis of late‑onset hypogonadism and a discussion about testosterone therapy.
Source: Male hypogonadism: recommendations from the Fifth International Consultation on Sexual Medicine (ICSM 2024), International Society for Sexual Medicine, 2025, https://doi.org/10.1093/sxmrev/qeaf036
TODO: consider adding scripts/calc.py for the icsm-testosterone-threshold-loh calculator
