What endocrine problems can cause small testicles and testicular pain in an adult or adolescent male?

Endocrine Causes of Small Testicles and Testicular Pain

Hypogonadism is the primary endocrine disorder causing small testicles, though it typically does not cause acute testicular pain—when pain is present alongside small testes, you must urgently rule out testicular torsion or epididymitis before attributing symptoms solely to an endocrine etiology. 1, 2

Primary Endocrine Disorder: Hypogonadism

Hypogonadism causes testicular atrophy (small testicles) and can be either primary (testicular failure) or central (hypothalamic-pituitary dysfunction). 3, 4

Clinical Presentation of Hypogonadism

• Small, soft testes on palpation are a hallmark finding during physical examination 1
• Secondary sexual characteristics should be assessed, including body hair distribution and breast development (gynecomastia may indicate estrogen excess) 1
• Body habitus changes including loss of muscle mass and increased adiposity 4, 5
• Sexual dysfunction including loss of libido and erectile dysfunction 4, 5
• Systemic symptoms such as diminished intellectual capacity, depression, lethargy, and osteoporosis 4

Laboratory Evaluation for Hypogonadism

An endocrine evaluation should be performed when sperm concentration is less than 10 million per mL, sexual function is impaired, or clinical findings suggest endocrinopathy. 1

• Minimal initial testing includes serum testosterone and follicle-stimulating hormone (FSH) levels 1
• Low testosterone with elevated FSH indicates primary hypogonadism (testicular failure) 3, 4
• Low testosterone with low or normal FSH indicates central hypogonadism (hypothalamic-pituitary dysfunction) 3, 4

Critical Distinction: Testicular Pain Requires Urgent Evaluation

Testicular pain is NOT a typical feature of hypogonadism alone—when present, it signals a potentially surgical emergency that must be evaluated immediately. 2, 6

Urgent Differential Diagnosis for Testicular Pain

• Testicular torsion presents with sudden onset of severe pain, negative Prehn sign (pain not relieved by elevation), and requires surgical intervention within 6-8 hours to prevent testicular loss 2, 6
• Epididymitis/epididymo-orchitis is the most common cause of testicular pain in adults, with gradual onset, positive Prehn sign, and increased blood flow on Doppler ultrasound 2, 6, 7
• Torsion of testicular appendage is most common in prepubertal boys but can occur in adolescents, may show "blue dot sign" visible through skin 2, 6

Immediate Diagnostic Algorithm for Testicular Pain

1. Duplex Doppler ultrasound is first-line imaging with 69-96.8% sensitivity and 87-100% specificity for testicular torsion 2, 7
2. Key ultrasound findings for torsion include decreased or absent blood flow, "whirlpool sign" of twisted spermatic cord, and enlarged heterogeneous testis 2
3. Key ultrasound findings for epididymitis include enlarged epididymis with increased blood flow on color Doppler and scrotal wall thickening 2, 7
4. Immediate urological consultation is mandatory when torsion cannot be excluded, as imaging should never delay surgical exploration when clinical suspicion is high 2, 6

Clinical Algorithm: Small Testicles WITH Pain

When a patient presents with both small testicles and testicular pain, follow this sequence:

1. First, rule out surgical emergencies (torsion, severe infection) with immediate physical examination focusing on onset of pain (sudden vs. gradual), Prehn sign, and cremasteric reflex 2, 6
2. Obtain urgent Doppler ultrasound to assess testicular perfusion and identify structural abnormalities 2, 7
3. If torsion is suspected clinically, proceed directly to surgical exploration without waiting for imaging 2, 6
4. Once acute pathology is excluded, perform endocrine evaluation with testosterone and FSH levels to assess for hypogonadism 1

Clinical Algorithm: Small Testicles WITHOUT Pain

For isolated small testicles without acute pain:

1. Measure testicular size by palpation during physical examination 1
2. Assess secondary sexual characteristics including hair distribution, muscle mass, and breast development 1
3. Obtain serum testosterone and FSH levels as the minimal initial endocrine workup 1
4. If sperm concentration is less than 10 million per mL or sexual dysfunction is present, proceed with comprehensive endocrine evaluation 1

Important Clinical Pitfalls

• Never attribute acute testicular pain to hypogonadism alone—this can lead to catastrophic delay in diagnosing torsion 2, 6
• Hypogonadism affects up to 5% of the male population and is frequently under-diagnosed 8, 9
• False-negative Doppler ultrasounds occur in up to 30% of torsion cases, particularly with partial torsion—clinical judgment supersedes imaging 2
• Normal urinalysis does not exclude testicular torsion or epididymitis 2
• The 6-8 hour window for testicular salvage in torsion is critical—any delay significantly increases risk of testicular loss 2, 6