A 12-year-old patient presents with severe thirst and large volumes of dilute urine. Which hypothalamic nucleus is likely affected?

The symptoms of severe thirst and large volumes of dilute urine are characteristic of diabetes insipidus, which often results from a deficiency in antidiuretic hormone (ADH), also known as vasopressin. The supraoptic nucleus of the hypothalamus plays a crucial role in the synthesis of ADH. When this nucleus is damaged or affected, it can lead to insufficient production of ADH, causing the kidneys to excrete large volumes of dilute urine and trigger a strong sensation of thirst in response to the body's need to compensate for the loss of water.

The supraoptic nucleus is specifically involved in the regulation of water balance by controlling the secretion of ADH from the posterior pituitary gland. Therefore, when there is an issue with this nucleus, the resultant hormonal imbalance leads to the severe thirst and polyuria observed in the patient.

In contrast, the other hypothalamic nuclei mentioned are involved in different functions. The anterior nucleus is mainly associated with thermoregulation, the dorsomedial nucleus is involved in feeding and aggression behaviors, and the ventromedial nucleus plays a role in satiety and energy balance. None of these nuclei directly influence the production of ADH related to the symptoms presented in this case.