Low testosterone

What it is

Low testosterone — clinically called hypogonadism or testosterone deficiency syndrome — affects an estimated 2–4% of adult men, with prevalence rising sharply after age 40 as testosterone declines at roughly 1–2% per year from the mid-30s onward. Hypogonadism is the formal medical term for a state in which the gonads (testes in men, ovaries in women) produce insufficient sex hormones to maintain normal physiological function. In Canada, testing is typically ordered through LifeLabs or Dynacare, with total testosterone drawn on two separate mornings — levels consistently below 10.4 nmol/L (300 ng/dL) alongside symptoms are the standard diagnostic threshold used by most Canadian endocrinologists, consistent with Endocrine Society guidance.

Testosterone is not exclusively a male hormone. In men, the testes produce approximately 95% of circulating testosterone; the adrenal glands contribute the remainder. In women, the ovaries and adrenal glands together produce smaller but physiologically meaningful amounts. In both sexes, testosterone supports libido, energy, mood, muscle mass, bone density, and cognitive function.

Causes and mechanism

Low testosterone arises through two distinct pathways, plus a third age-related pattern:

Type	Origin	Key LH/FSH pattern	Common causes
Primary hypogonadism	Testicular failure	LH and FSH elevated	Klinefelter syndrome (XXY), orchitis, testicular trauma, chemotherapy or radiation, autoimmune failure
Secondary hypogonadism	Pituitary or hypothalamic signalling failure	LH and FSH low or normal	Pituitary tumour, Kallmann syndrome, hyperprolactinaemia, opioid use, anabolic steroid use, obesity
Late-onset (age-related)	Gradual physiological decline	Variable	Aging, metabolic syndrome, obesity

Obesity deserves particular attention: aromatase enzyme in adipose tissue converts testosterone to estrogen, and the resulting estrogen excess suppresses the hypothalamic-pituitary-gonadal (HPG) axis, further reducing testosterone output. Opioid medications — widely prescribed in Canada — suppress gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion, making opioid-induced hypogonadism an underrecognized clinical problem.

In women, testosterone can fall abruptly after bilateral oophorectomy (surgical menopause), with premature ovarian insufficiency (POI), adrenal insufficiency, or hyperprolactinaemia. Oral contraceptives raise sex hormone-binding globulin (SHBG), which reduces free (bioavailable) testosterone even when total levels appear normal.

Symptoms and diagnosis

In men, symptoms include reduced or absent libido, erectile dysfunction, loss of morning erections, fatigue, decreased muscle mass and strength, increased abdominal fat, reduced bone density, low mood or irritability, difficulty concentrating, reduced body and facial hair, and gynecomastia (breast tissue development).

In women, the picture is subtler: persistent low libido, unexplained fatigue, reduced sense of wellbeing, and decreased muscle tone — often occurring alongside low estrogen symptoms after surgical menopause or POI.

Diagnostic workup in men follows a structured sequence:

1. Total testosterone — two separate morning draws (8–10 a.m.), fasting. Below 10.4 nmol/L (300 ng/dL) with symptoms supports deficiency.
2. Free testosterone and SHBG — clarifies bioavailable hormone when total testosterone is borderline.
3. LH and FSH — distinguishes primary (elevated) from secondary (low or normal) hypogonadism.
4. Prolactin — screens for hyperprolactinaemia.
5. Thyroid function, HbA1c, lipid panel — associated metabolic assessment.

Symptoms alone are not sufficient for diagnosis; two confirmed low morning readings are required before treatment is initiated.

Treatment options

Testosterone replacement therapy (TRT) is the primary treatment for symptomatic, confirmed testosterone deficiency. Delivery options include intramuscular or subcutaneous injections (most common in Canada), transdermal gels, adhesive patches, and oral testosterone undecanoate. Benefits across trials include improved libido, energy, mood, body composition, bone mineral density, and cognitive function. TRT suppresses the pituitary's LH output, which halts natural sperm production — men who want to preserve fertility should not start TRT without specialist input.

Fertility-preserving alternatives include:

• Clomiphene citrate or enclomiphene — stimulates the pituitary to increase LH, raising endogenous testosterone without suppressing spermatogenesis.
• Human chorionic gonadotropin (HCG) — mimics LH to stimulate testicular testosterone production; often combined with clomiphene for men who want to maintain fertility.

Lifestyle modification is clinically meaningful: weight loss in men with obesity can raise testosterone substantially by reducing aromatization and relieving HPG suppression. Resistance training, adequate sleep (7–9 hours), and stress reduction all support testosterone production and should be part of any management plan.

In women, low-dose testosterone therapy — typically a compounded cream or gel at physiological female doses — is used off-label for sexual dysfunction and significant fatigue. The Endocrine Society and The Menopause Society both recognize evidence supporting its use for hypoactive sexual desire disorder in postmenopausal women, though Health Canada has not approved a testosterone product specifically for women.

Canadian patients can access assessment and TRT through their family physician, an endocrinologist, or telehealth platforms such as Felix, Maple, Phoenix, Cleo, or Science & Humans — comparing cost, formulary access, and follow-up protocols across providers is worthwhile before committing to a program.

When to see a clinician in Canada

Men should seek evaluation for persistent reduced libido, erectile dysfunction combined with loss of morning erections, unexplained fatigue and muscle loss, or mood changes that do not resolve with lifestyle changes. Conditions such as Klinefelter syndrome, pituitary disease, or a history of chemotherapy warrant proactive testosterone assessment.

Women should seek evaluation after surgical menopause or a diagnosis of premature ovarian insufficiency if they experience persistent low libido and fatigue that is not explained by low estrogen alone.

Because testosterone levels fluctuate throughout the day and between days, a single low result is not sufficient — two separate morning draws are required before a diagnosis is confirmed and treatment is started.

Limitations and open questions

Research is still emerging on several fronts. The optimal testosterone threshold for initiating TRT in older men remains debated; the Endocrine Society's 2018 guideline acknowledges that evidence for cardiovascular benefit or risk with TRT in men over 65 is inconclusive. The TRAVERSE trial (2023) provided reassuring short-term cardiovascular safety data for TRT in middle-aged men with hypogonadism and elevated cardiovascular risk, but long-term data beyond a few years are limited.

For women, Health Canada has not approved any testosterone product specifically for female use, meaning all prescribing is off-label and dosing relies on compounded formulations without standardized pharmacokinetic data. The long-term safety of testosterone therapy in women — particularly regarding breast cancer risk — has not been established in large randomized trials.

The relationship between testosterone and depression is bidirectional and incompletely understood: it is not yet clear whether treating borderline-low testosterone in men with primary depressive disorder produces clinically meaningful mood benefit independent of antidepressant therapy. Clinicians should not substitute TRT for evidence-based depression treatment.