I've noticed my testicles have decreased in size and no longer become firm during erection; could this be testicular atrophy and what evaluation is needed?

Testicular Size Changes and Evaluation

Your symptoms—decreased testicular size, lack of firmness during erection, and a "lighter" feeling—warrant immediate evaluation with scrotal ultrasound and hormonal testing (FSH, LH, testosterone) to quantify testicular volume and assess for testicular atrophy, which is definitively present when volume falls below 12 mL. 1

Understanding Your Symptoms

Normal Testicular Changes During Erection

• The cremasteric reflex normally causes testicular retraction and firmness during sexual arousal, and loss of this response combined with perceived size reduction suggests possible testicular atrophy or reduced testicular reserve. 1
• Testicular volumes below 12 mL are definitively considered atrophic and associated with impaired spermatogenesis, elevated FSH levels, and increased risk of intratubular germ cell neoplasia. 1

Clinical Significance of Size Changes

• Testicular volume strongly correlates with total sperm count and sperm concentration—volumes below 12 mL warrant investigation for fertility concerns and underlying pathology. 1
• A size discrepancy between testes greater than 2 mL or 20% requires ultrasound evaluation to exclude masses, varicocele, or other structural abnormalities. 1

Essential Diagnostic Workup

Immediate Testing Required

• Scrotal ultrasound with high-frequency probes (>10 MHz) to accurately measure testicular volume using the Lambert formula (Length × Width × Height × 0.71), as the traditional ellipsoid formula systematically underestimates volume by 20-30%. 1
• Morning serum FSH, LH, and total testosterone drawn between 08:00-10:00 hours on at least two separate occasions to establish reliable baseline values and distinguish primary testicular failure from secondary causes. 1
• Semen analysis to correlate testicular volume with actual reproductive function, as volume alone cannot definitively predict fertility status. 1

Interpretation of Results

• Elevated FSH (>7.6 IU/L) with testicular volume <12 mL indicates reduced testicular reserve and impaired spermatogenic capacity, representing primary testicular dysfunction. 1, 2
• Normal or low LH with low testosterone suggests secondary hypogonadism from pituitary dysfunction, requiring prolactin measurement. 1
• Elevated LH and FSH with low testosterone confirms primary testicular failure. 1

High-Risk Scenarios Requiring Urgent Evaluation

Cancer Risk Stratification

• Men under 30-40 years with testicular volume <12 mL carry a ≥34% risk of intratubular germ cell neoplasia (TIN) in the contralateral testis if testicular cancer develops. 1
• Untreated TIN progresses to invasive testicular cancer in approximately 70% of cases within 7 years. 1
• History of cryptorchidism (undescended testicles) combined with volume <12 mL markedly increases cancer risk and mandates intensified surveillance with testicular self-examination. 1

Red-Flag History Elements to Report

• Prior undescended testes dramatically raises risk of atrophy and testicular cancer. 1
• Use of anabolic steroids, testosterone, opioids, or glucocorticoids can cause reversible testicular atrophy. 1
• History of scrotal trauma—testicular atrophy occurs in 50% of patients following blunt scrotal trauma. 3
• Prior inguinal hernia repair—testicular atrophy can result from thrombosis of spermatic cord veins during surgical dissection. 4
• Chemotherapy or pelvic radiation causes irreversible testicular shrinkage. 1

Common Causes of Testicular Atrophy

Primary Testicular Dysfunction

• Klinefelter syndrome (47,XXY) is the most common genetic cause, presenting with testicular volume <12 mL and elevated FSH—karyotype testing is mandatory when these findings coexist. 1
• Bilateral cryptorchidism, especially when uncorrected or surgically corrected after puberty, markedly increases atrophy risk. 1
• Varicocele causes progressive testicular damage through venous congestion—palpable varicoceles with abnormal semen parameters benefit from surgical repair. 1, 5

Secondary Testicular Dysfunction

• Chronic opioid use suppresses GnRH secretion, resulting in low gonadotropins and bilateral atrophy. 1
• Anabolic steroid or exogenous testosterone use causes complete suppression of spermatogenesis and persistent atrophy for months to years after cessation. 1
• Hyperprolactinemia from pituitary adenoma or medications leads to secondary hypogonadism and shrinkage. 1

Systemic Conditions

• Type 2 diabetes/metabolic syndrome is linked to functional hypogonadism and reduced volume. 1
• Chronic liver disease (cirrhosis) contributes to secondary hypogonadism. 1
• HIV infection causes both primary and secondary gonadal dysfunction. 1

Fertility Preservation Considerations

Immediate Actions if Volume <12 mL Confirmed

• Bank sperm immediately—collect 2-3 separate ejaculates with 2-3 days abstinence between collections to provide insurance against technical failures or poor post-thaw recovery. 1
• Never start testosterone replacement without clarifying fertility intentions, as exogenous testosterone causes azoospermia that may take months to years to recover. 1
• Avoid all anabolic steroids, opioids, and gonadotoxic medications to prevent further decline. 1

Sperm Retrieval Options if Azoospermia Develops

• Microsurgical testicular sperm extraction (micro-TESE) achieves 40-50% sperm retrieval rates even with elevated FSH and small testicular volume, and is 1.5 times more successful than conventional TESE. 1, 2

Critical Pitfalls to Avoid

• Do not dismiss symptoms as "normal variation"—progressive testicular atrophy requires investigation, especially when accompanied by loss of cremasteric response during erection. 1
• Do not delay evaluation if you are under 30-40 years old—the cancer risk with small testes in this age group is substantial. 1
• Do not start testosterone therapy before completing fertility evaluation—this will eliminate any remaining sperm production. 1
• Do not rely on a single hormone measurement—FSH and testosterone should be measured on at least two separate mornings. 1

Monitoring and Follow-Up

• Repeat semen analysis every 6-12 months to detect early decline in sperm parameters, as single analyses can be misleading due to natural variability. 1
• Teach yourself testicular self-examination given increased cancer risk with smaller volumes. 1
• Recheck hormones after 3-6 months if reversible causes (thyroid dysfunction, metabolic syndrome) are addressed. 1