What lab work is recommended for new onset gynecomastia?

Laboratory Workup for New Onset Gynecomastia

For new onset gynecomastia, a comprehensive laboratory evaluation should include testosterone, estradiol, LH, FSH, TSH, prolactin, hCG, AFP, and liver and renal function tests to identify underlying pathological conditions. 1, 2

Initial Assessment Considerations

• Gynecomastia is defined as actual glandular breast tissue enlargement, distinct from pseudogynecomastia (fatty tissue deposition) 1
• Proper investigation may reveal an underlying pathology in 45-50% of adult cases 2
• Laboratory testing should be targeted based on clinical suspicion after thorough history and physical examination 2

Recommended Laboratory Tests

Hormonal Evaluation

• Testosterone (T): To assess for hypogonadism
• Estradiol (E2): To evaluate for increased estrogen levels
• Sex hormone-binding globulin (SHBG): To determine bioavailable testosterone
• Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH): To differentiate primary from secondary hypogonadism
• Thyroid-stimulating hormone (TSH): To rule out hyperthyroidism
• Prolactin: To assess for hyperprolactinemia

Tumor Markers

• Human chorionic gonadotropin (hCG): To screen for testicular and other germ cell tumors
• Alpha-fetoprotein (AFP): To screen for testicular tumors

Metabolic Assessment

• Liver function tests: To evaluate for liver disease (cirrhosis can cause hormonal imbalances)
• Renal function tests: To assess for renal insufficiency
• Morning urine and serum osmolality: If there are symptoms suggesting endocrine disorders 3

Special Considerations

• Testicular ultrasound is recommended as the detection of testicular tumors by palpation has low sensitivity 2
• For men ≥25 years with breast pain, diagnostic mammography or digital breast tomosynthesis is recommended as the initial imaging study 1
• Core needle biopsy should be performed if clinical picture is suspicious for malignancy 2

Algorithm for Laboratory Workup

1. Basic hormonal panel: Testosterone, estradiol, LH, FSH, TSH, prolactin
2. Tumor markers: hCG, AFP (particularly important in younger men)
3. Metabolic assessment: Liver and renal function tests
4. Additional tests based on clinical suspicion:
   • Karyotype if gonadoblastoma is suspected in pre-pubertal patients
   • Adrenal function tests if Cushing's syndrome is suspected
   • Drug screening if medication or substance abuse is suspected

Common Pitfalls to Avoid

• Don't assume medication-induced gynecomastia precludes further investigation; a detailed workup is still warranted 2
• Don't overlook testicular examination and ultrasound, as testicular pathology is an important cause of gynecomastia
• Don't delay evaluation in adults, as proper investigation may reveal underlying pathology in nearly half of cases 2
• Don't forget to consider common medications (spironolactone, antipsychotics, 5-α reductase inhibitors) as potential causes 1

By systematically evaluating these laboratory parameters, clinicians can identify the underlying cause of gynecomastia and develop an appropriate treatment plan that addresses the root cause rather than just the symptoms.