What are the indications, recommended dosing, monitoring, and risks of testosterone replacement therapy for middle‑aged men (≈40–65 years) with confirmed low testosterone?

Testosterone Replacement Therapy in Middle-Aged Men: Indications and Risks

Testosterone replacement therapy should be offered to middle-aged men with confirmed low testosterone (typically <300 ng/dL on two early-morning measurements) who have sexual dysfunction and desire improvement in sexual function, but should NOT be routinely prescribed for nonspecific symptoms like fatigue, low energy, or cognitive complaints. 1

Diagnostic Requirements

Before initiating therapy, you must confirm:

• Two separate early-morning total testosterone measurements showing levels consistently below 300 ng/dL (some guidelines use 280-350 ng/dL thresholds) 2
• Presence of specific symptoms, particularly sexual dysfunction (decreased libido, erectile dysfunction) 1, 3
• Measurement of LH and FSH to distinguish primary from secondary hypogonadism 3

Critical pitfall: Do not screen asymptomatic men or rely on a single testosterone measurement 3. Age-related decline alone (approximately 1.6% per year starting in the mid-30s) is not an indication for treatment 1.

When to Prescribe: The Evidence-Based Algorithm

OFFER testosterone therapy for:

• Men with confirmed low testosterone AND sexual dysfunction who want to improve sexual function 1
• Men with organic hypogonadism (identifiable hypothalamic-pituitary-testicular axis disease) 4

DO NOT prescribe testosterone for:

• Improving energy, vitality, physical function, or cognition—the evidence shows these benefits are uncertain and low-quality 1
• Men planning fertility in the near term (testosterone suppresses spermatogenesis) 3
• Routine use in all men ≥65 years with low testosterone 3

The ACP guideline is explicit here: their Recommendation 2 states clinicians should NOT initiate testosterone to improve energy, vitality, physical function, or cognition, as the evidence is insufficient 1. This directly contradicts common prescribing patterns but represents the highest-quality guideline evidence.

Absolute Contraindications

Do not prescribe if the patient has 3:

• Breast or prostate cancer
• PSA >4 ng/mL (or >3 ng/mL with high prostate cancer risk without urological evaluation)
• Palpable prostate nodule or induration
• Elevated hematocrit
• Untreated severe obstructive sleep apnea
• Severe lower urinary tract symptoms
• Uncontrolled heart failure
• MI or stroke within the last 6 months
• Thrombophilia

Formulation Selection

Intramuscular testosterone is preferred over transdermal formulations because costs are considerably lower while clinical effectiveness and harms are similar 1. However, long-acting intramuscular formulations carry the highest risk of erythrocytosis 2.

Alternative formulations include transdermal patches/gels, buccal testosterone, and pellets. Selection should consider patient preference, pharmacokinetics, and cost 3, 5.

Monitoring Protocol

Initial monitoring (first 12 months):

• Reassess symptoms at 12 months—discontinue if no improvement in sexual function 1
• At 3 months: Check serum testosterone, hematocrit, and PSA 3, 5
• Target testosterone levels: Mid-normal range (450-600 ng/dL) 6

Ongoing monitoring (annually thereafter):

• Serum testosterone levels
• Hematocrit (watch for erythrocytosis)
• PSA in men ≥40 years 5
• Symptom improvement and adverse effects
• Treatment adherence 3

Cardiovascular Safety: The Most Recent Evidence

The cardiovascular risk profile is reassuring but nuanced. A 2025 meta-analysis of 23 RCTs involving 9,280 men found that testosterone therapy does NOT increase all-cause mortality, cardiovascular mortality, stroke, or myocardial infarction 7. However, there was a significant increase in cardiac arrhythmias (RR 1.53) 7.

This contradicts older concerns about cardiovascular harm and aligns with recent large trials showing no increased risk of MI or stroke, even in high-risk patients 5. The Endocrine Society guideline from 2018 recommends against use within 6 months of MI or stroke as a precautionary measure 3.

Other Key Risks

• Erythrocytosis: Most common adverse effect, particularly with intramuscular formulations; requires hematocrit monitoring 2, 6
• Prostate concerns: No evidence of increased prostate cancer risk, but requires PSA monitoring 6, 5
• Fertility suppression: Testosterone suppresses spermatogenesis—critical counseling point for men of reproductive age 3
• Sleep apnea: May worsen untreated obstructive sleep apnea 3

Clinical Benefits When Appropriately Prescribed

In men with confirmed hypogonadism and sexual dysfunction, evidence supports 2, 6, 5:

• Improved sexual function (strongest evidence)
• Increased lean body mass and reduced fat mass
• Metabolic benefits: Decreased waist circumference, improved insulin sensitivity (especially with lifestyle interventions)
• Improved bone mineral density
• Modest improvements in mood and energy in select patients

Important caveat: These benefits are most pronounced in men with true organic hypogonadism, not age-related decline alone 4.

The Shared Decision-Making Discussion

You must explicitly discuss 1:

• Potential benefits are primarily for sexual function
• Uncertain benefits for energy, vitality, and cognition
• Risk of cardiac arrhythmias
• Need for ongoing monitoring
• Cost considerations (intramuscular is cheaper)
• Fertility implications
• 12-month trial period with discontinuation if ineffective

The guideline framework prioritizes sexual dysfunction as the primary indication because this is where the evidence is strongest, albeit still low-certainty 1. The ACP's conditional recommendations reflect that individual patient values and preferences matter significantly in this decision.