Secondary Hypogonadism in Australian Men: Causes, Diagnosis, and Treatment
Key Takeaways
Secondary hypogonadism — low testosterone caused by the brain, not the testes — is the most common and most reversible form of testosterone deficiency in Australian men. Here's what causes it and how it's treated.
Primary vs Secondary Hypogonadism: The Key Distinction
Primary hypogonadism originates in the testes. The testes are damaged or dysfunctional and cannot produce adequate testosterone despite normal pituitary signalling. LH and FSH are elevated.
Secondary hypogonadism originates in the brain. The hypothalamus or pituitary fails to produce sufficient GnRH, LH, and FSH to stimulate the testes. LH and FSH are low or inappropriately normal. The testes themselves are intact and capable of responding if given the right hormonal signal.
| LH/FSH | Testosterone | |
|---|---|---|
| Primary hypogonadism | High | Low |
| Secondary hypogonadism | Low or normal | Low |
This is why LH and FSH are essential components of any testosterone assessment — you cannot distinguish primary from secondary hypogonadism on testosterone alone.
The Most Common Causes of Secondary Hypogonadism in Australia
1. Obesity and Metabolic Syndrome
The most prevalent cause in Australian clinical practice. The Endocrine Society estimates that 30–50% of men with obesity have hypogonadism. The Endocrine Society of Australia (MJA, 2016) recommends weight loss as the primary intervention before TRT is initiated.
2. Obstructive Sleep Apnoea
Testosterone is primarily synthesised during sleep — particularly during REM cycles. A 2021 study in Frontiers in Endocrinology confirmed significant correlation between OSA severity and reduced testosterone. Effective CPAP treatment can meaningfully improve testosterone in men with OSA-related secondary hypogonadism.
3. Hyperprolactinaemia (Prolactinoma)
A prolactin-secreting pituitary adenoma suppresses GnRH secretion — one of the most important reversible causes of secondary hypogonadism. Hormones Australia identifies hyperprolactinaemia as a key differential. Treatment with dopamine agonists typically resolves the prolactinoma and restores testosterone without TRT.
4. Opioid-Induced Hypogonadism
Opioid analgesics suppress GnRH secretion and cause dose-dependent testosterone suppression. The Australian Prescriber specifically lists opioid medications as a cause of secondary hypogonadism.
5. Anabolic Steroid Use (Prior)
Men who have used anabolic steroids recreationally — particularly for extended periods — present with secondary hypogonadism that can persist for months to years after cessation. Recovery can be supported pharmacologically with HCG and SERMs.
6. Idiopathic (Unknown Cause)
A significant proportion of secondary hypogonadism in middle-aged men has no identifiable underlying cause (idiopathic hypogonadotrophic hypogonadism) and is managed with TRT or — in men desiring fertility — HCG and FSH therapy.
Treatment: When to Address the Cause vs When to Start TRT
For secondary hypogonadism with a reversible cause: address the cause first where clinically feasible.
- Obesity → structured weight loss
- OSA → CPAP therapy
- Prolactinoma → cabergoline
- Opioid-induced → dose review and opioid rotation if possible
- Post-steroid → HCG and/or clomiphene
For secondary hypogonadism without a reversible cause, or where lifestyle intervention has failed after 3–6 months: TRT is appropriate and supported by the Endocrine Society's 2018 Clinical Practice Guidelines.
References
- Bhasin S, et al. Testosterone Therapy in Men with Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018.
- Endocrine Society of Australia — MJA position statement.
- Australian Prescriber — Low testosterone in men.
- Hormones Australia — Hypogonadism.
- Healthdirect Australia — Obstructive Sleep Apnoea.
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