Hypothalamus Functions

Which hypothalamic nucleus is primarily responsible for the regulation of circadian rhythm and sleep-wake cycles?

A 52-year-old man is brought to the emergency department following a motor vehicle accident with a severe head injury and basilar skull fracture. Within 4 hours, he develops polyuria (urine output 400 mL/hour), polydipsia, and serum sodium of 152 mEq/L (normal 135–145). Urine osmolality is 150 mOsm/kg (normal 300–900), and serum osmolality is 310 mOsm/kg. Administration of desmopressin (synthetic ADH) results in a decrease in urine output and normalization of serum sodium. Which hypothalamic nucleus is most likely damaged?

Which hormone is released by the hypothalamus in response to cold exposure and acts on the anterior pituitary to stimulate thyroid hormone secretion?

A 38-year-old woman presents to the endocrinology clinic with a 6-month history of amenorrhea, galactorrhea, and weight gain of 8 kg despite dietary restriction. She denies headaches or visual disturbances. On examination, blood pressure is 128/82 mmHg, BMI 31 kg/m², and bilateral breast tenderness is noted. Serum prolactin is elevated at 85 ng/mL (normal <25 ng/mL), and TSH is normal. MRI pituitary shows a 12 mm sellar mass. Which hypothalamic hormone is most likely deficient in this patient?