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: A

Rationale: The correct answer is A: Ventilation. Ventilation is the process of moving air into the lungs and distributing it to the alveoli for gas exchange. Choice B, Aeration, is not the correct term for this specific process. Choice C, Enclosure vapor, is not related to the movement of air into the lungs. Choice D, Residual volume, refers to the amount of air left in the lungs after maximal expiration and is not the process of moving air into the lungs.

Correct Answer: C

Rationale: Reperfusion injury refers to the secondary injury that occurs after blood flow is reestablished following ischemia. This process leads to tissue damage due to the sudden reintroduction of oxygen and nutrients, causing oxidative stress, inflammation, and cell death. Choice A is incorrect as it describes the normal healing process of bone tissue after a fracture. Choice B is incorrect as it describes specific mechanisms related to skin wounds, not reperfusion injury. Choice D is incorrect as it refers to a different concept, which is adverse reactions or complications that can occur after a blood transfusion, not reperfusion injury.

Correct Answer: B

Rationale: Disseminated intravascular coagulation (DIC) is characterized by simultaneous clotting and bleeding throughout the body. This imbalance in the body's clotting system leads to the formation of blood clots in small blood vessels, which can consume clotting factors and platelets, ultimately leading to excessive bleeding. Choices A, C, and D are incorrect because they do not describe the characteristic feature of DIC, which involves both clotting and bleeding.

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.

Correct Answer: C

Rationale: The correct answer is C. Osteoporosis is commonly caused by bone loss that occurs with aging, leading to brittle bones. Choice A, poor nutrition in infancy, is not a direct cause of osteoporosis. Choice B, regularly weight-bearing exercise, actually helps in maintaining bone density and strength, reducing the risk of osteoporosis. Choice D, cerebral palsy and associated disorders, is not a common cause of osteoporosis.

Correct Answer: A

Rationale: The correct answer is A. Persistent chest pain that may radiate to the arm is a classic symptom of myocardial infarction. This pain is typically described as crushing, pressure-like, or squeezing. Choice B is incorrect because brief sternal chest pain on inspiration is not characteristic of myocardial infarction. Choice C is incorrect because rapid respirations with left-sided weakness and numbness are not typical symptoms of myocardial infarction. Choice D is incorrect because left upper quadrant abdominal pain that radiates to the back and shoulder is not a common presentation of myocardial infarction.

Correct Answer: C

Rationale: The correct answer is C: Weakness and confusion. Hypoglycemia is characterized by low blood sugar levels, leading to inadequate glucose supply to the brain, resulting in symptoms like weakness and confusion. Choices A, B, and D are incorrect. Rapid, deep breathing is not typically a sign of hypoglycemia but can be seen in other conditions like respiratory issues. Increased urination is more commonly associated with conditions like diabetes mellitus, while high blood pressure is not a typical sign of hypoglycemia.

Correct Answer: A

Rationale: The correct answer is A: Tachycardia. Tachycardia, which is an increased heart rate, is a classic clinical manifestation of hyperthyroidism. In hyperthyroidism, there is an excess production of thyroid hormones, leading to an increased metabolic rate. This increased metabolism can cause symptoms such as a rapid heart rate. Choices B, C, and D are incorrect because constipation, weight gain, and fatigue are more commonly associated with hypothyroidism, where there is a deficiency of thyroid hormones leading to a slower metabolic rate.