ITE Endocrinology and Metabolism 4

Question 1

A 30-year-old man presents with polyuria, polydipsia, and a serum sodium of 148 mEq/L.
Urine osmolality is 110 mOsm/kg after water deprivation, rising to 680 mOsm/kg after desmopressin (DDAVP).
What is the diagnosis?

Accepted Answer

Central (neurogenic) diabetes insipidus

Answer

Nephrogenic diabetes insipidus

Answer

Primary polydipsia

Answer

Syndrome of inappropriate ADH

Question 2

A 58-year-old woman on long-term lithium therapy presents with fatigue and a calcium of 10.8 mg/dL. PTH is 72 pg/mL (high-normal). What is the most likely mechanism of her hypercalcemia?

Accepted Answer

Lithium raises the calcium set-point for PTH suppression

Answer

Lithium-induced autonomous parathyroid adenoma

Answer

Lithium causes vitamin D toxicity

Answer

Lithium induces ectopic PTH production

Question 3

A 26-year-old woman with type 1 diabetes presents with recurrent DKA episodes despite good outpatient compliance. She has celiac antibodies positive on screening. How does undiagnosed celiac disease contribute to DKA in type 1 diabetes?

Accepted Answer

Malabsorption leads to unpredictable glucose-insulin matching

Answer

Celiac disease causes insulin resistance

Answer

Celiac increases glucagon secretion

Answer

Celiac destroys beta cells directly

Question 4

A 65-year-old man with metastatic lung cancer develops calcium of 13.5 mg/dL, low PTH, low 1,25-dihydroxyvitamin D, and elevated PTHrP. Which mechanism best explains his hypercalcemia?

Accepted Answer

Humoral hypercalcemia of malignancy via PTHrP

Answer

Local osteolytic metastases releasing calcium

Answer

Ectopic 1-alpha hydroxylase activity

Answer

Adrenal insufficiency from metastases

Question 5

A 40-year-old woman has an incidentally discovered 2.5 cm adrenal mass on CT for kidney stones. She has no hypertension or symptoms. Hormonal workup shows: normal aldosterone/renin ratio, normal 24-hour urine catecholamines, and 1 mg overnight dexamethasone suppression test shows cortisol of 3.8 mcg/dL. What is the next step?

Accepted Answer

Repeat imaging in 6–12 months and reassay hormones annually

Answer

Adrenalectomy

Answer

PET scan to rule out malignancy

Answer

Salivary cortisol testing

Question 6

A 22-year-old woman with Turner syndrome (45,X) presents for routine evaluation. Which endocrine complication is she at highest risk for?

Accepted Answer

Primary hypothyroidism (Hashimoto's)

Answer

Cushing syndrome

Answer

Primary hyperparathyroidism

Answer

Prolactinoma

Question 7

A 55-year-old man has low serum testosterone (180 ng/dL), LH 0.8 mIU/mL (low), and FSH 1.0 mIU/mL (low). MRI pituitary is normal. He takes opioids chronically for back pain. What is the diagnosis?

Accepted Answer

Opioid-induced hypogonadotropic hypogonadism

Answer

Primary hypogonadism

Answer

Klinefelter syndrome

Answer

Idiopathic hypogonadotropic hypogonadism