Gynecomastia, a benign enlargement of the male breast due to proliferation of the glandular component, is a common clinical condition with various causes. This study investigates the changes of serum sexual hormones levels and the causes of patients with gynecomastia.

The conditions associated with gynecomastia were evaluated in 68 gynecomastia patients. The levels of serum estradiol (E2), and testosterone (T), and the estradiol to testosterone (E2/T) ratio were measured in 37 of these 68 subjects along with 10 healthy male controls. Ultrasound for the adrenal gland and liver diseases, liver function test, and physical examination or ultrasound for testicular pathology were also performed.

The most common cause of gynecomastia was idiopathic (50.0%). The conditions associated with gynecomastia were drugs (23.5%), hormone (10.3%), and various associated diseases (16.2%) including liver diseases (8.8%), chronic lung diseases (4.4%), lung cancer (1.5%) and chronic renal failure (1.5%). The levels of E2 and T, and the E2 to T ratio in the control group were 35.3±3.9 pg/ml, 5.0±0.4 ng/ml and 7.1±0.5 respectively. Those in the gynecomastia group were 48.7±7.1 pg/ml, 4.3±0.3 ng/ml and 12.0±1.8 respectively. The differences between the two groups for the E2 to T ratio as well as the levels of E and T were not significant, though the average E2 level and the E2 to T ratio in the gynecomastia group were higher than those in the control group. The causes of gynecomastia varied according to the patient age.

The differences of the E2 to T ratio, and the level of E2 and T in the patients with gynecomastia were not the only cause of gynecomastia. Thus, considerations need to be given to the changes of sexual hormones as well as associated diseases or drugs to enable better understanding of the causes of gynecomastia.