Which of the following is a cause of hypothyroidism?

Correct Answer: B

Rationale: The correct answer is B: Autoimmune destruction of the thyroid gland. In hypothyroidism, the thyroid gland does not produce enough hormones to meet the body's needs. This can be due to autoimmune destruction of the thyroid gland, where the body's immune system mistakenly attacks the thyroid tissue. Choices A, C, and D are incorrect. Overproduction of cortisol is associated with conditions like Cushing's syndrome, overactivity of the thyroid gland is a characteristic of hyperthyroidism, and insufficient iodine intake can lead to goiter but not necessarily hypothyroidism.

Correct Answer: B

Rationale: A pulmonary embolism is commonly caused by a blood clot that originates in the venous system of the lower extremity and travels to the lungs, blocking blood flow. This clot is known as a venous thromboembolism. An autoimmune disorder (Choice A) is not typically associated with pulmonary embolism. Intracranial pressure (Choice C) refers to pressure inside the skull and is unrelated to pulmonary embolism. Hypotension (Choice D) is low blood pressure and is not a common cause of pulmonary embolism.

Correct Answer: A

Rationale: Renin is the correct answer. When arterial blood pressure decreases, the kidneys release renin, which triggers a series of reactions ultimately leading to an increase in blood pressure and peripheral resistance. Antidiuretic hormone (choice B) is involved in water retention, atrial natriuretic hormone (choice C) promotes sodium excretion and lowers blood pressure, and insulin (choice D) regulates glucose metabolism, not blood pressure.

Correct Answer: A

Rationale: The correct answer is A: Respiratory acidosis. In respiratory acidosis, there is an accumulation of CO2 in the blood, leading to a decrease in pH. The elevated PaCO2 of 55 mmHg in the given results indicates hypoventilation, causing respiratory acidosis. Choices B, C, and D are incorrect because the provided data does not show metabolic acidosis, respiratory alkalosis, or metabolic alkalosis.

Correct Answer: A

Rationale: The correct answer is Parathyroid hormone (Choice A). Parathyroid hormone plays a key role in regulating calcium levels in the blood. When there is an imbalance in parathyroid hormone secretion, it can lead to increased calcium levels in the blood. Antidiuretic hormone (Choice B) is involved in regulating water balance, not calcium levels. Calcitonin (Choice C) helps lower blood calcium levels and is unlikely to cause an increase. Melatonin (Choice D) regulates sleep-wake cycles and does not have a direct effect on calcium levels in the blood.