Gynecomastia is a medical term for benign breast enlargement in males. The condition is signified by an increase in the mass of glandular tissue in the breast. Significant male breast enlargement is diagnosed when the breast tissue diameter is at least two centimeters (2 cm). The presence of gynecomastia may be unilateral or bilateral, physiologic or pathologic, or even idiopathic, but is mostly multifactorial.
In younger patients, breast enlargement is usually unilateral; in the case of adult patients, it’s mostly bilateral. The Pathologic type is due to alteration of activity or production of the sex hormones, namely estrogen and testosterone. Androgen activity is decreased, with increased androgen aromatization to estrogen – this causes higher estrogen level and activity in the peripheral tissues, predominantly in the breast. Certain conditions are associated with these hormonal changes, such as hypogonadism, chronic liver disease, renal impairments, and thyroid problems.
In patients diagnosed with hyperthyroidism as a single disease entity, male breast enlargement is not a common occurrence. More frequently, males afflicted with both hyperthyroidism and breast enlargement have other endocrinological problems, such as hypogonadism. A medical research conducted recently revealed that pubertal or adolescent male patients with noticeable breast enlargement have increased free T3 (triiodothyronine), but this can be explained by the increased basal metabolic rate during the younger years. However some experts have observed that about 10-40% of hyperthyroid males in general end up suffering from breast enlargement.
Thyroid hormone production is controlled by the feedback mechanisms happening between the hypothalamus, the thyroid gland, and the pituitary gland. Thyrotropin-releasing hormone (TRH) from the hypothalamus influences the release of thyroid-stimulating hormone (TSH) from the pituitary gland. TSH then binds to the receptors present in the thyroid gland to release the thyroid hormones free T4 (thyroxine) and T3 (triiodothyronine) to the peripheral circulation. Normally, when enough levels of thyroid hormones are present in the periphery, negative feedback mechanism to the hypothalamus occurs, decreasing the production of TRH.
In hyperthyroidism, this negative feedback is disturbed in a manner of numerous pathological processes. Disturbance of the normal physiologic hypothalamic-pituitary- thyroid gland axis can be due to the disorder of each of the organs involved, but in many ways they result into increase levels of peripheral thyroid hormones that are free to bind to other globular proteins in the many organs of the body, in turn increasing the basal metabolic rate. Increase serum thyroid hormone activity may influence sex hormone production – peripheral aromatase activity increases, leading to lower testosterone- estrogen ratio. Also, sex hormone binding globulin (SHBG) levels increase, resulting in lower free testosterone level – this causes feminization in males. Moreover, hyperthyroid males have increased levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH), negatively affecting the production and activity of the sex hormones.
In summary, hyperthyroidism may present with breast enlargement, but is not commonly the general cause. Most hyperthyroid males with gynecomastia has primary or secondary hypogonadism, aside from their hyperthyroid state. Considering other conditions such as testicular dysfunction, malnutrition, and others may cause this symptom. Clinical examination by a medical professional, laboratory work-up, and imaging may be necessary to know the root cause of the disorder.
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