Ginekomastia

01Pathophysiology

Gynecomastia results from a relative or absolute increase in estrogen activity compared to androgen activity at the level of breast tissue. The male breast contains estrogen receptors that, when stimulated, trigger ductal epithelial hyperplasia and stromal proliferation. Under normal conditions, the predominance of androgens suppresses this estrogenic effect. When that balance tips, breast tissue grows.

Physiologic gynecomastia occurs in three well-defined life stages. In neonates, transplacental maternal estrogens drive transient breast enlargement that resolves within weeks. During puberty, the adrenal glands and testes produce estrogen precursors (particularly androstenedione and DHEA), and peripheral aromatization in adipose tissue converts these androgens into estradiol. Because testicular testosterone production has not yet reached full adult levels, this temporary estrogen surge causes breast tissue growth that typically resolves within 6 to 24 months. In elderly men, declining testosterone production combined with increased peripheral aromatization from greater adiposity creates the same imbalance.

Pathologic gynecomastia occurs through several mechanisms. Increased estrogen production can come from estrogen-secreting tumors (testicular Leydig or Sertoli cell tumors, adrenal tumors) or from hCG-secreting tumors (testicular germ cell tumors, extragonadal choriocarcinoma) that stimulate Leydig cells to produce more estrogen. Decreased androgen production occurs in primary hypogonadism (Klinefelter syndrome being the classic board-relevant example) or secondary hypogonadism. Liver cirrhosis contributes through two pathways: the liver fails to clear estrogens adequately, and sex hormone-binding globulin (SHBG) rises, binding free testosterone preferentially and leaving more bioavailable estrogen. Chronic kidney disease causes both decreased testosterone clearance of gonadotropins and Leydig cell dysfunction.

Drug-induced gynecomastia is among the most tested categories. Spironolactone blocks androgen receptors and inhibits testosterone synthesis. Ketoconazole inhibits cytochrome P450 enzymes involved in steroidogenesis. Cimetidine acts as an androgen receptor antagonist. Marijuana contains phytoestrogens. Digoxin has structural similarity to estradiol and binds estrogen receptors. Anabolic steroids undergo peripheral aromatization to estrogens. The key teaching point is that the mechanism varies by drug, but the final common pathway is always the same: estrogen effect exceeds androgen effect at the breast.

02Classification and Clinical Manifestation

Severity

03Diagnostic Workup

The first and most important step is a thorough physical examination. True gynecomastia presents as a palpable, concentrically located rubbery disc directly beneath the areola. It moves with the overlying skin when pinched. This must be distinguished from pseudogynecomastia (lipomastia), where the enlargement is due to adipose tissue without glandular proliferation, seen in obese males. The key discriminator on exam: pseudogynecomastia lacks that firm subareolar disc.

If the patient is a pubertal male aged 10-14 with bilateral tender breast tissue, no testicular abnormality on exam, and no red flag features, this is most likely physiologic and requires no further workup. Reassurance and follow-up are sufficient.

When the presentation is atypical (rapid onset, unilateral, associated with testicular mass, or in a non-physiologic age group), a hormonal panel is the next step. The pattern of testosterone, LH, and FSH helps localize the problem. An elevated beta-hCG is a red flag for germ cell tumor and demands testicular ultrasound. Elevated estradiol without an obvious drug cause should prompt imaging of the testes and adrenals to search for an estrogen-secreting tumor.

The most critical exam distinction is gynecomastia versus male breast cancer. Breast cancer in males presents as a hard, fixed, eccentric (not centered on the areola) mass, often with skin retraction, nipple discharge (especially bloody), or axillary lymphadenopathy. Any of these features mandates mammography or breast ultrasound followed by biopsy.

04Management and Treatment

Observation is the appropriate management for physiologic gynecomastia. In pubertal boys, over 90% of cases resolve within 2 years without intervention. Parents and patients need reassurance that this is a normal developmental variant.

When a drug is identified as the cause, the first step is always to discontinue or replace the offending medication. This is the classic "next best step" tested on exams. If the medication cannot be stopped (e.g., spironolactone in a patient with heart failure and no alternative), then medical treatment of the gynecomastia itself may be warranted.

Tamoxifen is the most effective pharmacologic option. As a selective estrogen receptor modulator, it competitively blocks estrogen receptors in breast tissue. It is most effective when gynecomastia is of recent onset (less than 12 months), because the tissue is still in the florid/proliferative phase with active ductal epithelial hyperplasia. Once the tissue transitions to the fibrotic phase (after 12 months), it becomes resistant to medical therapy because the glandular tissue has been replaced by dense stroma and fibrosis. This is why prolonged gynecomastia requires surgical excision rather than medication.

Aromatase inhibitors such as anastrozole reduce peripheral conversion of androgens to estrogens. They have shown benefit in some studies of pubertal gynecomastia but the evidence is less robust than for tamoxifen.

Surgical excision is reserved for cases that have persisted beyond 12-24 months (fibrotic phase), failed medical therapy, or cause significant psychological distress. Liposuction may be added for contouring when there is a combined glandular and adipose component.

For pathologic causes, treatment is directed at the underlying condition. Testicular tumors require orchiectomy. Hypogonadal patients may benefit from testosterone replacement, though exogenous testosterone can paradoxically worsen gynecomastia initially through peripheral aromatization to estradiol. Klinefelter patients with gynecomastia should be monitored more closely because they carry a 20 to 50-fold increased risk of male breast cancer compared to the general male population.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students miss gynecomastia questions is by failing to distinguish true gynecomastia from pseudogynecomastia and from male breast cancer. The exam loves to present an obese male with bilateral breast enlargement and test whether you recognize that without a firm subareolar disc, this is lipomastia requiring weight management rather than a hormonal workup. Conversely, when they present an older male with a hard, eccentric, fixed breast mass, the answer is mammography and biopsy for suspected carcinoma, not reassurance.

The second major trap involves drug-induced gynecomastia. When the vignette includes a medication history featuring spironolactone, cimetidine, ketoconazole, digoxin, or marijuana, the next best step is discontinuing the agent, not ordering an extensive hormonal panel. Students who jump to labs before addressing the obvious pharmacologic cause lose easy points.

Another frequently tested concept is the florid versus fibrotic phase distinction. A question may describe gynecomastia present for 2 years and ask about treatment. Tamoxifen is wrong here because the tissue is fibrotic and will not respond to medical therapy. The answer is surgical excision.

Finally, remember the Klinefelter association. A tall male with small firm testes, infertility, learning difficulties, and gynecomastia should prompt you to think 47,XXY. And critically, Klinefelter patients with gynecomastia have a substantially elevated risk of breast cancer, making it a condition where new breast changes warrant closer evaluation rather than simple reassurance.