Final answer:
The initial laboratory evaluation for gynecomastia of unknown origin includes tests measuring liver enzymes, renal function, thyroid function, and hormone levels such as testosterone, LH, estradiol, and hCG to assess potential underlying causes.
Step-by-step explanation:
When the etiology of gynecomastia is not clinically apparent, the initial laboratory evaluation typically includes the measurement of serum levels of liver enzymes, renal function, thyroid function, and hormones such as testosterone, luteinizing hormone (LH), estradiol, and human chorionic gonadotropin (hCG).
These tests are performed because gynecomastia can be associated with liver diseases, renal diseases, thyroid disorders, and hormone imbalances. Specifically, abnormal levels of hormones can promote the development of breast tissue in males, leading to gynecomastia. It is important to assess these parameters to determine the underlying cause of the breast enlargement and to guide further diagnostic and therapeutic measures.