A 29-year-old man comes to the office due to progressive headaches, fatigue, and visual disturbances for the past 6 weeks. He was diagnosed with sarcoidosis a year ago after having a dry cough and hypercalcemia. The patient's condition was treated with oral glucocorticoid therapy, which was discontinued after 6 months due to improvement in symptoms. Physical examination reveals bitemporal defects on visual field testing but is otherwise normal. Laboratory studies again show mild hypercalcemia, but the remainder of the values, including complete blood count, serum glucose, creatinine, and electrolytes, are within normal reference ranges. MRI of the brain reveals a soft tissue mass involving the hypothalamus and pituitary stalk. Which of the following pituitary hormones is most likely elevated in this patient?

Question

A 29-year-old man comes to the office due to progressive headaches, fatigue, and visual disturbances for the past 6 weeks.  He was diagnosed with sarcoidosis a year ago after having a dry cough and hypercalcemia.  The patient's condition was treated with oral glucocorticoid therapy, which was discontinued after 6 months due to improvement in symptoms.  Physical examination reveals bitemporal defects on visual field testing but is otherwise normal.  Laboratory studies again show mild hypercalcemia, but the remainder of the values, including complete blood count, serum glucose, creatinine, and electrolytes, are within normal reference ranges.  MRI of the brain reveals a soft tissue mass involving the hypothalamus and pituitary stalk.  Which of the following pituitary hormones is most likely elevated in this patient?

Quizplus · Accepted Answer

11ec160b_3abc_9004_9249_bfe4fee61ba3_MD0001_00 This patient with sarcoidosis has a hypothalamic and pituitary stalk mass with mass-effect symptoms (eg, headache, bitemporal visual field defects). In combination with the recurrent hypercalcemia (caused by excessive calcitriol formation by activated macrophages) 6 months after the discontinuation of glucocorticoid therapy, this presentation suggests active sarcoidosis with involvement of the hypothalamus (neurosarcoidosis). Although sarcoidosis classically causes noncaseating granulomas involving the lungs, lymph nodes, and skin, granulomas can form in any tissue. Mass lesions in the hypothalamus or pituitary stalk can disrupt the hypothalamic-pituitary axis by obstructing the hypophyseal portal system. Unlike other pituitary hormones, prolactin release is negatively regulated by dopamine produced in the hypothalamus. Dopamine acts on the dopamine D2 receptors of lactotrophs, the prolactin-producing cells of the pituitary. Disruption of dopaminergic pathways (eg, by an infiltrating sarcoid lesion) in the pituitary stalk leads to loss of inhibition and a subsequent increase in prolactin. (Choices A, B, and D) Pituitary adenomas can cause excess hormone formation; however, this patient has a hypothalamic mass, not a pituitary adenoma. In contrast to prolactin, other pituitary hormones (ACTH, growth hormone, thyrotropin [TSH], LH, and FSH) are inhibited by hypothalamic lesions because the dominant effect of the hypothalamus on them is stimulatory. Although abruptly discontinuing an oral glucocorticoid can cause adrenal insufficiency with a subsequent increase in ACTH, low blood pressure, hypoglycemia, hyponatremia, and hyperkalemia would be expected. In addition, adrenal insufficiency typically occurs rapidly after glucocorticoid withdrawal (not 6 months later). (Choice E) Vasopressin is produced in the supraoptic and paraventricular nuclei of the hypothalamus and transported to the posterior pituitary for release. Lesions of the hypothalamus and pituitary stalk can decrease vasopressin levels. Mass lesions in the central nervous system can cause vasopressin secretory dysregulation, leading to the syndrome of inappropriate antidiuretic hormone (SIADH) with euvolemic hyponatremia. However, the normal sodium levels in this patient exclude this syndrome. Educational objective: The release of prolactin is under inhibitory control by dopamine secretion from the hypothalamus. Disruption of dopaminergic pathways or blockade of dopamine D2 receptors can cause hyperprolactinemia.

A 29-Year-Old Man Comes to the Office Due to Progressive