Male Hypogonadism: Open Controversies in the Field

Why the Definition of Male Hypogonadism Is Still Contested

Male hypogonadism lacks a universally accepted biochemical definition, and that gap drives nearly every downstream controversy. The 2018 Endocrine Society Clinical Practice Guideline recommends confirming total testosterone below 300 ng/dL on two morning samples before initiating testosterone replacement therapy (TRT) [1]. The American Urological Association (AUA) aligns with this threshold [2]. Yet the European Association of Urology sets its cutoff at 12 nmol/L (roughly 346 ng/dL), creating a zone of 46 ng/dL where a man is hypogonadal by European standards but normal by American ones [3].

Why a Single Number Is Insufficient

Testosterone is highly pulsatile. A 2017 analysis published in the Journal of Clinical Endocrinology and Metabolism (JCEM) found that intra-individual variation in morning total testosterone can exceed 20% on repeat testing [4]. A man measured at 295 ng/dL on Monday may read 340 ng/dL on Wednesday, which means the two-sample rule required by guidelines still misclassifies a meaningful minority of patients.

Assay platform adds a second layer of error. Immunoassay methods, the dominant approach in community laboratories, show systematic bias compared with liquid chromatography-tandem mass spectrometry (LC-MS/MS). In a head-to-head comparison across 9 platforms, immunoassay readings diverged from LC-MS/MS reference values by up to 30% in the hypogonadal range [5].

The Free Testosterone Problem

Total testosterone captures protein-bound fractions that are biologically inactive. Free testosterone, roughly 2 to 3% of the total, reflects the hormonally active pool. Equilibrium dialysis (ED) is the accepted reference method for free testosterone, but it is expensive, slow, and unavailable at most commercial labs [6]. Calculated free testosterone, derived from total testosterone and sex hormone-binding globulin (SHBG), introduces its own errors because SHBG assays themselves vary across platforms.

A man with normal total testosterone but elevated SHBG, which is common in aging and liver disease, may have genuinely low free testosterone yet receive no diagnosis. The Endocrine Society acknowledges this gap but stops short of mandating free testosterone measurement in all patients [1].

The Cardiovascular Risk Debate

Cardiovascular safety is the most clinically consequential unresolved question in TRT, and it took a 5,000-patient randomized trial to begin settling it.

TRAVERSE: What the Trial Found and What It Did Not

The TRAVERSE trial (NCT03518034, N=5,204) enrolled men aged 45 to 80 with hypogonadism and pre-existing cardiovascular disease or high cardiovascular risk. Randomized to testosterone undecanoate gel or placebo and followed for a median of 33 months, the TRT group showed a 7.0% rate of major adverse cardiovascular events (MACE) versus 7.3% in the placebo group, meeting the pre-specified non-inferiority margin [7]. The FDA cited TRAVERSE in its 2023 updated labeling communication as evidence against a blanket cardiovascular contraindication in hypogonadal men with documented disease [8].

Two findings from TRAVERSE deserve specific attention. First, atrial fibrillation occurred in 3.5% of the testosterone group versus 2.4% of the placebo group (P<0.05), a signal that did not meet the primary endpoint threshold but was pre-specified as a secondary outcome [7]. Second, pulmonary embolism trended higher in the TRT arm, though the absolute numbers were small. Whether these signals represent true drug effects or chance findings in a high-risk population remains open.

Earlier Observational Data and the Vigen Controversy

Before TRAVERSE, the field was shaped by a 2013 JAMA observational study by Vigen et al. (N=8,709) that reported a 25.7% absolute increase in adverse cardiovascular events with TRT in veterans with coronary artery disease [9]. The paper triggered an FDA safety review. Subsequent re-analyses found methodological flaws, including patients counted in the TRT group who never filled their prescriptions [10]. The Vigen study illustrates how observational data in this field consistently generate more questions than answers.

Erythrocytosis as a Cardiovascular Mediator

TRT reliably raises hematocrit. The Endocrine Society guideline flags a hematocrit above 54% as a reason to reduce dose or withhold therapy [1]. In TRAVERSE, polycythemia occurred in 21.3% of the TRT group versus 12.5% with placebo [7]. Elevated hematocrit raises blood viscosity and thrombotic risk, connecting TRT mechanistically to pulmonary embolism and deep vein thrombosis. Most prescribers monitor hematocrit at 3 and 6 months post-initiation, then annually, yet agreement on what to do at hematocrit readings between 50 to 54% is inconsistent across guidelines.

Late-Onset Hypogonadism in Men Over 65: Treat or Observe?

Testosterone declines roughly 1 to 2% per year after age 30 [11]. By age 70, a substantial fraction of men fall below the 300 ng/dL threshold on biochemistry alone, even without classic symptoms. This creates the late-onset hypogonadism (LOH) debate.

The Testosterone Trials (TTrials) Evidence

The Testosterone Trials were a coordinated set of seven double-blind, placebo-controlled studies in men aged 65 and older with total testosterone below 275 ng/dL. The Sexual Function Trial (N=790) showed that testosterone gel (1.62%) improved sexual desire and erectile function compared with placebo over 12 months [12]. The Physical Function Trial did not show a significant improvement in walking speed. The Cognitive Function Trial reported no benefit on memory or executive function [12].

Bone mineral density did increase in the Bone Trial arm, and anemia improved in men with unexplained anemia [12]. The composite picture from TTrials is that TRT in older men benefits sexual symptoms and anemia but not the broader functional or cognitive endpoints that clinicians and patients often hope for.

When Symptoms and Biochemistry Diverge

A man aged 72 with a total testosterone of 260 ng/dL but no sexual symptoms, no fatigue, and normal bone density presents a clinical dilemma. Treating purely on biochemistry risks unnecessary polycythemia, potential atrial fibrillation, and suppression of residual spermatogenesis. Withholding treatment ignores a confirmed biochemical deficiency. The Endocrine Society states that treatment should require "both consistently low testosterone levels and signs and symptoms of androgen deficiency" [1]. But the definition of "consistent" symptoms is subjective, and no validated symptom instrument has been adopted universally.

The Aging Males' Symptoms (AMS) scale and the Androgen Deficiency in Aging Males (ADAM) questionnaire are used clinically, but both have sensitivity above 80% with specificity below 40% for biochemical hypogonadism [13]. A positive questionnaire does not reliably identify a man who will respond to TRT.

Fertility Preservation and TRT: An Underappreciated Conflict

Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal axis. Within 6 weeks of starting TRT, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) drop sharply, reducing intratesticular testosterone and impairing spermatogenesis. Azoospermia or severe oligospermia develops in most men on TRT within 3 to 6 months [14].

Recovery After TRT Cessation

Spermatogenesis recovers in most men after stopping TRT, but recovery is not universal or rapid. A 2020 systematic review in Fertility and Sterility found median time to recovery of sperm concentration to 20 million/mL was approximately 6 months, but 10 to 15% of men failed to recover within 24 months [14]. Age above 35 and TRT duration above 36 months were associated with slower or incomplete recovery.

For hypogonadal men who want future fertility, clomiphene citrate (50 mg on alternate days) or human chorionic gonadotropin (hCG, 500 to 1,000 IU three times weekly) can raise testosterone while preserving sperm production. Neither drug carries FDA approval specifically for male hypogonadism, making them off-label options. The Endocrine Society guideline explicitly recommends against TRT in men actively trying to conceive [1].

The Information Gap at the Point of Prescribing

A 2019 survey published in Urology found that fewer than one-third of men started on TRT by primary care physicians recalled being counseled about fertility effects [15]. This represents a practical informed-consent failure that persists across practice settings, regardless of what guidelines recommend.

Prostate Cancer Risk: Saturation Theory vs. Residual Uncertainty

For decades, a diagnosis of prostate cancer was an absolute contraindication to TRT. The rationale traced to Charles Huggins's 1941 Nobel Prize-winning observation that castration caused prostate cancer regression. By extension, restoring testosterone seemed logically dangerous.

The Saturation Model

Abraham Morgentaler proposed the androgen receptor saturation model: prostate androgen receptors reach maximal stimulation at relatively low testosterone concentrations (roughly 150 to 200 ng/dL in prostate tissue). Above that level, additional testosterone produces little incremental prostate stimulation. This model predicts that raising testosterone from 200 to 600 ng/dL carries minimal prostate risk [16].

Observational data from Morgentaler's cohort and several retrospective series suggest TRT in men treated for low-risk prostate cancer does not accelerate biochemical recurrence. The 2018 Endocrine Society guideline softened its language, classifying prostate cancer as a relative rather than absolute contraindication in selected patients with adequately treated, low-risk disease [1].

What Remains Genuinely Unknown

No prospective randomized trial has specifically enrolled prostate cancer survivors and compared TRT to placebo with cancer recurrence as a primary endpoint. TRAVERSE excluded men with active prostate cancer. The saturation model is biologically plausible but rests primarily on retrospective data and mechanistic inference. PSA velocity on TRT should be monitored at 3 and 12 months post-initiation, with urologic referral if PSA rises more than 1.4 ng/mL within any 12-month period per AUA guidance [2].

Screening in Asymptomatic Men: A Policy Controversy

Population-level testosterone screening has not been endorsed by any major U.S. Guideline body. The USPSTF has not issued a formal recommendation statement on testosterone deficiency screening, effectively leaving it without explicit support or condemnation at the federal advisory level [17].

Who Is Driving Prescribing Volume

TRT prescriptions in the United States rose from roughly 1.3 million in 2010 to over 3.8 million in 2018, a nearly threefold increase driven substantially by direct-to-consumer marketing and telehealth platforms [18]. A significant share of these prescriptions were written for men with testosterone above 300 ng/dL or without a confirmed symptomatic indication.

The Endocrine Society's position is direct: "We suggest against making a diagnosis of androgen deficiency in men with no symptoms or signs consistent with testosterone deficiency" [1]. The AUA echoes this, requiring documented symptoms plus confirmed biochemical deficiency before initiating TRT [2]. Nevertheless, prescribing patterns suggest a meaningful portion of clinical practice diverges from these recommendations.

Conflicts of Interest in Research Funding

A 2016 analysis in JAMA Internal Medicine examined funding sources for TRT trials and found that industry-sponsored studies reported significantly more favorable outcomes than non-industry studies [19]. This funding bias complicates the interpretation of the existing evidence base. It does not mean industry-funded trials are wrong, but it justifies particular scrutiny of effect sizes when the sponsor has a commercial interest in a positive result.

Measurement Controversies: Which Assay, Which Time of Day, Which Sample?

Morning sampling is standard because testosterone peaks between 7:00 and 10:00 a.m. And troughs in late afternoon, with a diurnal amplitude of 25 to 35% in younger men [20]. Older men show a blunted diurnal rhythm, raising the question of whether afternoon sampling in men above 65 produces meaningfully different clinical classifications.

LC-MS/MS vs. Immunoassay

LC-MS/MS is the only assay method endorsed by the Endocrine Society for diagnostic confirmation when immunoassay results are ambiguous [1]. The cost differential is real: immunoassay panels run $20 to 50 in most U.S. Commercial labs, while LC-MS/MS typically costs $80 to 150. Most insurance plans reimburse either, but access to LC-MS/MS varies substantially outside academic medical centers.

The CDC's Hormone Standardization (HoSt) Program has worked to reduce between-laboratory variation in testosterone assays, but participation is voluntary. As of 2023, not all high-volume commercial labs have achieved HoSt certification [21].

The following decision framework summarizes the diagnostic pathway most consistent with converging guideline evidence:

Step 1. Obtain two morning (before 10:00 a.m.) total testosterone samples at least one week apart using LC-MS/MS when immunoassay reads 250 to 400 ng/dL.

Step 2. If total testosterone is confirmed below 300 ng/dL, measure LH and FSH to distinguish primary from secondary hypogonadism.

Step 3. If SHBG is abnormal (elevated in aging, liver disease; low in obesity, type 2 diabetes), calculate free testosterone using the Vermeulen formula or measure directly by equilibrium dialysis.

Step 4. Document at least two consistent symptoms using the AMS or ADAM scale, acknowledging their low specificity.

Step 5. Discuss fertility goals explicitly before any TRT prescription. If fertility is desired, refer to a reproductive urologist before initiating testosterone.

Specific Open Research Gaps

Several questions remain without adequate trial data as of mid-2025.

Long-term TRT outcomes beyond 5 years are almost entirely unknown. TRAVERSE ran for a median of 33 months [7]. The TTrials ran for 12 months [12]. No randomized data characterize 10-year cardiovascular, prostate, or cognitive outcomes.

The optimal testosterone target range during TRT has no consensus. The Endocrine Society recommends targeting mid-normal range (400 to 700 ng/dL) without specifying a minimum effective concentration [1]. Whether maintaining 400 ng/dL produces the same sexual and bone outcomes as maintaining 650 ng/dL has not been tested.

The role of TRT in metabolic disease remains unresolved. Men with type 2 diabetes and hypogonadism show higher insulin resistance and worse glycemic control than eugonadal diabetic men [22]. Whether TRT improves HbA1c or insulin sensitivity in this subgroup, beyond the effect of weight loss, requires a dedicated trial. The TRAVERSE data included glycemic outcomes but were not powered to detect differences specifically in the diabetic subpopulation.

Racial and ethnic differences in testosterone reference ranges have been insufficiently studied. Several analyses suggest Black men have modestly higher mean testosterone than white men at comparable ages, raising questions about whether a race-neutral threshold of 300 ng/dL applies uniformly [23]. No major guideline has stratified its diagnostic threshold by race, in part due to insufficient data to do so responsibly.