TSH is produced by the pituitary gland and regulates thyroid hormone production. It's the primary screening test for thyroid dysfunction. High TSH suggests hypothyroidism (underactive thyroid), while low TSH suggests hyperthyroidism.
Thyroid dysfunction shares many symptoms with hypogonadism, including fatigue, weight gain, depression, and low libido, making it essential to rule out or co-manage alongside TRT. Subclinical hypothyroidism (TSH 4-10 mIU/L) is common and can blunt the benefits of TRT.