ABSTRACT
The pituitary gland lies in the sella turcica which is situated in the middle cranial fossa at the base of brain. Pituitary masses may present with a typical clinical syndrome resulting from hypersecretion of one or more anterior pituitary hormones. Alternatively, they may present through compression of surrounding structures such as the optic chiasm or the adjacent normal pituitary, causing hypopituitarism. Age- and gender-matched serum insulin-like growth factor- 1 (IGF-I) levels are elevated in acromegaly. Consequently, an IGF-I level provides a useful laboratory screening measure when clinical features raise the possibility of acromegaly. The diagnosis of Cushing's syndrome is based on laboratory documentation of endogenous hypercortisolism. Thyroid-stimulating hormone (TSH)-producing macroadenomas are rare but are often large and locally invasive when they occur. Patients usually present with thyroid goitre and hyperthyroidism, reflecting overproduction of TSH. Diagnosis is based on demonstrating elevated serum free T4 levels, inappropriately normal or high TSH secretion, and magnetic resonance imaging (MRI) evidence of a pituitary adenoma.
