A 55-year-old man has experienced increasing lethargy for the past 7 months. Physical examination shows hyperpigmentation of the skin. Vital signs include temperature of 36.9°C, pulse of 70/min, respirations of 14/min, and blood pressure of 95/65 mm Hg. Laboratory studies include a serum cortisol level of 3 μg/mL at 8:00 am with a serum corticotropin level of 65 pg/mL. Which of the following diseases most often occurs in patients with this disorder?

Correct Answer: C

Rationale: Addison disease (primary chronic adrenocortical insufficiency) most often results from an idiopathic autoimmune condition (in areas of the world where the incidence of active tuberculosis is low). Autoimmune adrenalitis is associated with the appearance of other autoimmune diseases in about half of all cases. Such autoimmune phenomena are frequently seen in other endocrine organs, such as the thyroid gland.

Correct Answer: C

Rationale: Left anterior descending (LAD), not circumflex, is most commonly blocked in MI.

Correct Answer: D

Rationale: All are true: biconcave shape aids gas exchange, flexibility, and rouleaux formation.

Correct Answer: A

Rationale: NK cells are innate, targeting infected/cancer cells; others are adaptive (T/B) or phagocytic.

Correct Answer: D

Rationale: Bronchioles regulate airflow resistance via smooth muscle constriction/dilation.