Pituitary adenomas: an overview.

Prolactinomas and nonfunctioning adenomas are the most common types of pituitary adenomas. Patients with pituitary adenomas may present initially with symptoms of endocrine dysfunction such as infertility, decreased libido, and galactorrhea, or with neurologic symptoms such as headache and visual changes. The diagnosis may also be made following imaging done for an unrelated issue in an asymptomatic patient; this is termed a pituitary incidentaloma. Oversecretion of hormones from a dysfunctional pituitary gland may result in classic clinical syndromes, the most common of which are hyperprolactinemia (from oversecretion of prolactin), acromegaly (from excess growth hormone), and Cushing disease (from overproduction of adrenocorticotropic hormone). In the diagnostic approach to a suspected pituitary adenoma, it is important to evaluate complete pituitary function, because hypopituitarism is common. Therapy for pituitary adenomas depends on the specific type of tumor, and should be managed with a team approach to include endocrinology and neurosurgery when indicated. Dopamine agonists are the primary treatment for prolactinomas. Small nonfunctioning adenomas and prolactinomas in asymptomatic patients do not require immediate intervention and can be observed.

Symptomatic hyponatremia in association with a low-iodine diet and levothyroxine withdrawal prior to I131 in patients with metastatic thyroid carcinoma.

BACKGROUND: Strategies to improve I131 uptake in thyroid carcinoma include levothyroxine (LT4) withdrawal or thyrotropin (TSH) administration along with a low-iodine diet. We report five patients with papillary or follicular thyroid carcinoma who developed symptomatic hyponatremia during LT4 withdrawal and low-iodine diet. RESULTS: Four patients had pulmonary and/or brain metastases. All had restricted iodine intakes during LT4 withdrawal. Presenting complaints included weakness, dizziness, fainting spells, lethargy, and/or nausea. Baseline serum sodium levels while on LT4 suppression were normal. During presentation all were hypothyroid and serum sodium ranged from 110 to 121 mmol/L (normal 135-148). Despite hyponatremia, the plasma renin activity and serum aldosterone levels were suppressed, indicating volume expansion. The hyponatremia responded to fluid restriction and normalized after LT4 replacement. Low sodium intake, inappropriate antidiuretic hormone secretion syndrome (SIADH)-like disorder secondary to hypothyroidism and/or lung or cerebral metastases may have contributed to hyponatremia. CONCLUSIONS: The development of hyponatremia during LT4 withdrawal and low-iodine diet in otherwise healthy patients with thyroid carcinoma is extremely rare. However, elderly patients with metastatic thyroid carcinoma need observation during LT4 withdrawal combined with a low-iodine diet and should receive instruction to take iodine-free sodium chloride. Free water restriction may be necessary in some patients.