Endocrinology Exam Questions

Correct Answer: A

Rationale: Oxytocin is a hormone produced by the hypothalamus and released by the pituitary gland. In the bloodstream, oxytocin is mostly bound to a carrier protein called neurophysin. This binding helps to protect oxytocin from being degraded too quickly in the bloodstream, thus allowing it to exert its effects on target tissues such as the uterus and mammary glands. Oxytocin plays important roles in stimulating uterine contractions during labor, facilitating milk letdown during breastfeeding, and promoting social bonding and emotional connections.

Correct Answer: B

Rationale: Small cell (oat cell) carcinoma of the lung is most commonly associated with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). This paraneoplastic syndrome occurs in patients with small cell lung cancer due to the production of antidiuretic hormone (ADH) by the tumor cells. The excessive release of ADH leads to water retention and dilutional hyponatremia, causing symptoms such as nausea, confusion, seizures, and potentially life-threatening complications. Other types of lung cancer, such as squamous cell carcinoma, large cell carcinoma, and adenocarcinoma, are less commonly associated with SIADH.

Correct Answer: A

Rationale: Acromegaly is the condition characterized by the enlargement of the bones of the hands, feet, and face due to the overproduction of growth hormone in adults. This excess growth hormone typically comes from a benign tumor in the pituitary gland, leading to the gradual enlargement of these body parts. Cushing syndrome, on the other hand, is caused by prolonged exposure to high levels of cortisol and is not directly related to bone enlargement. Gigantism is the condition of excessive growth in height due to overproduction of growth hormone occurring in children before the closure of growth plates. Myxedema is a term used to describe severe hypothyroidism and is not directly associated with bone enlargement.

Correct Answer: B

Rationale: Nephrogenic diabetes insipidus (NDI) is a condition where the kidneys are unable to respond to antidiuretic hormone (ADH) as they should, leading to excessive urination and extreme thirst. One of the main causes of nephrogenic diabetes insipidus is the use of certain medications, with lithium being the most common culprit. Lithium can interfere with the kidney's response to ADH, resulting in decreased water reabsorption and the characteristic symptoms of diabetes insipidus. Other causes of NDI can include genetic mutations affecting the vasopressin receptor gene or other underlying conditions such as hypercalcemia, hypokalemia, or obstructive uropathy.

Correct Answer: B

Rationale: Karyotype 47, XYY refers to the presence of an extra Y chromosome in males. This condition is known as XYY syndrome, also called Jacob's syndrome. Individuals with XYY syndrome are typically phenotypically male but may have some associated physical and behavioral characteristics. These individuals are often referred to as "supermales" due to the presence of the extra Y chromosome. This is different from true hermaphroditism, Klinefelter's syndrome, and gonadal dysgenesis, which have distinct chromosomal patterns and manifestations.