Synopsis
Confirm symptomatic testosterone deficiency with reliable repeated measurements, separate primary from hypothalamic-pituitary causes, and restore health without suppressing desired fertility or overlooking pituitary and testicular disease.
- Male hypogonadism requires compatible symptoms or signs plus consistently low testosterone; a single result in an asymptomatic or acutely unwell person is not the diagnosis.
- Obtain testosterone on two separate early-morning samples under appropriate fasting and stable-health conditions, using the local assay and reference range.
- Sex hormone-binding globulin alters total testosterone interpretation in obesity, liver disease, thyroid disease and some medicines; calculated free testosterone can help in borderline or discordant cases.
- High LH and FSH with low testosterone indicates primary testicular failure, whereas low or inappropriately normal gonadotrophins suggest hypothalamic-pituitary suppression or disease.
- Obesity, obstructive sleep apnoea, severe illness, undernutrition, opioids and anabolic steroid withdrawal can produce functional secondary hypogonadism; treat reversible drivers while excluding structural pathology.
- Very low testosterone with low gonadotrophins, raised prolactin, additional pituitary deficits, headache or visual symptoms requires pituitary evaluation rather than routine replacement alone.
- Exogenous testosterone suppresses LH, FSH and intratesticular testosterone and can cause azoospermia; do not use it when current biological fertility is desired.
- Before testosterone replacement, clarify fertility, prostate and breast symptoms, haematocrit, cardiovascular stability, sleep apnoea, lower urinary tract symptoms and product-specific contraindications.
- Monitor clinical benefit as well as serum testosterone, full blood count and prostate safety; stop or reformulate treatment when adverse effects or absent benefit outweigh gains.
Key red flags
Headache, visual field loss, diplopia, galactorrhoea, polyuria, adrenal or thyroid deficit and severe central biochemistry needs prompt pituitary investigation.
Thunderclap headache, visual loss, ophthalmoplegia, vomiting, hypotension or impaired consciousness is an endocrine and neurosurgical emergency with possible acute cortisol deficiency.
Investigation priorities
Confirm persistent biochemical deficiency under standardised conditions.
Management branches
Compatible sexual, reproductive, pubertal or skeletal features and an initial low result.
- Review timing, fasting, acute illness, sleep, alcohol, obesity, medicines, opioid or anabolic exposure and repeat an early-morning total testosterone under standardised stable conditions.
- Add SHBG and calculated free testosterone when total values are borderline or binding protein may be abnormal, using the laboratory's validated method.
- Measure LH and FSH to localise the axis, then prolactin and targeted pituitary, thyroid, iron or genetic tests according to the pattern.
- Do not start replacement until symptoms, repeated biochemistry, cause, fertility intention and baseline safety have been reconciled, unless specialist emergency care directs otherwise.
Key medicines
Transdermal testosterone gelApply the licensed daily starting amount to the specified clean dry skin and titrate from timed levels.Prevent transfer to partners or children by washing hands, covering the site and following product contact instructions. Monitor haematocrit, testosterone and prostate safety; skin irritation and adherence affect exposure.
Long-acting testosterone undecanoate injectionAdminister the licensed deep intramuscular loading and maintenance schedule by trained staff with timed monitoring.Observe product-specific post-injection precautions and avoid casual initiation because reversal is slow. Peaks, erythrocytosis, prostate concerns and changing fertility plans require review.