Spironolactone is a medication used to treat various conditions, including heart failure, high blood pressure, fluid retention, acne, and hair loss. A known side effect of this medication is gynecomastia, which refers to the enlargement of male breast tissue.
How Spironolactone Affects the Body
Spironolactone functions as a potassium-sparing diuretic, helping the body eliminate excess sodium and water while retaining potassium. It achieves this by blocking the action of aldosterone, a hormone that regulates salt and water balance in the kidneys. This diuretic effect is beneficial for conditions like high blood pressure and heart failure.
Beyond its diuretic properties, spironolactone also possesses anti-androgenic effects. Androgens are male hormones like testosterone. Spironolactone works by blocking androgen receptors, proteins on cells that androgens bind to. It also inhibits enzymes involved in the synthesis of androgens, further reducing their overall activity in the body.
The Hormonal Mechanism of Breast Tissue Growth
Spironolactone’s anti-androgenic actions contribute to gynecomastia by blocking androgen receptors in various tissues, including breast tissue. This prevents androgens from interacting with these receptors, reducing their influence on breast cells and creating a relative deficiency in androgenic activity within the body.
Male breast tissue contains both androgen and estrogen receptors. Estrogen, a female hormone, stimulates the growth of glandular breast tissue. The reduction in androgenic activity shifts the delicate balance between androgens and estrogens.
This hormonal imbalance, where estrogen’s effects become more prominent, can stimulate breast tissue growth. Spironolactone can also indirectly increase estrogen levels by enhancing the conversion of testosterone to estradiol in the body or by displacing estradiol from binding proteins. This combined effect of reduced androgen activity and potentially increased estrogen influence promotes the enlargement of male breast tissue, leading to gynecomastia.
How Common is Spironolactone-Induced Gynecomastia?
Gynecomastia is a well-documented side effect of spironolactone. The risk of gynecomastia is linked to spironolactone dosage and treatment duration. Higher doses, particularly above 150 mg daily, are associated with a higher likelihood of this side effect, affecting up to 52% of patients in some reports.
In a study of heart failure patients treated with spironolactone, approximately 9% of male subjects developed gynecomastia. The onset of breast enlargement can vary widely, appearing anywhere from one to two months to over a year after starting the medication. Older males may also be more susceptible, possibly due to naturally shifting hormone levels with age.
What to Do About Spironolactone-Induced Gynecomastia
If breast enlargement or tenderness occurs while taking spironolactone, consult a healthcare provider promptly. Open communication with your doctor allows for proper evaluation and discussion of treatment adjustments. Early intervention can lead to better outcomes.
Spironolactone-induced gynecomastia is often reversible, especially if addressed early. Discontinuing the medication or reducing the dosage can lead to a reduction or resolution of the breast enlargement. Resolution time varies, but pain typically subsides and swelling decreases within a month of stopping the drug.
Healthcare providers may consider alternative medications, such as eplerenone, a diuretic with a lower potential for causing gynecomastia. Eplerenone has a lower affinity for androgen receptors. In rare instances, if breast tissue becomes fibrous and persists despite medication changes, surgical options may be discussed.