Testosterone replacement therapy: role of pituitary and thyroid in diagnosis and treatment.

Crosstalk among hormones characterizes endocrine function, and assessment of the hypogonadal man should take that into consideration. In men for whom testosterone deficiency is a concern, initial evaluation should include a thorough history and physical exam in which other endocrinopathies are being considered. Hypogonadism can be associated with both pituitary and thyroid dysfunction, for which appropriate biochemical evaluation should be undertaken in certain clinical scenarios. If low serum testosterone is confirmed measurement of luteinizing and follicle stimulating hormones (LH and FSH respectively) is essential to establish whether the hypogonadism is primary or secondary. In secondary hypogonadism measurement of prolactin is always necessary, and measurement of other pituitary hormones, along with pituitary imaging, may be indicated. Checking thyroid function may also be enlightening, and can raise additional therapeutic considerations. Correction of other pituitary axes may attenuate the need for testosterone replacement therapy in some cases.