By definition, pituitary microadenomas are benign tumors of the pituitary gland that measure less than 10 mm in diameter. They generally come to medical attention due to signs and symptoms of endocrine dysfunction from excessive hormonal production, though some may be non-secretory, and thus, clinically silent. The most commonly secreted hormone is prolactin, resulting in galactorrhea, amenorrhea, infertility and loss of libido. Less commonly secreted hormones may include ACTH (resulting in Cushing's disease), growth hormone (resulting in acromegaly), TSH (resulting in hyperthryoidism), and the gonadotropins (resulting in sexual dysfunction and infertility).