Which of the following is the most common cause of Cushing's disease?

Correct Answer: A

Rationale: The most common cause of Cushing's disease is an ACTH-producing pituitary adenoma. In this condition, the pituitary gland produces excessive amounts of adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands to produce high levels of cortisol. This leads to the signs and symptoms of Cushing's disease, such as weight gain, high blood pressure, and muscle weakness. Adrenocortical adenoma refers to a benign tumor of the adrenal cortex that can also cause Cushing's syndrome, but it is not as common as an ACTH-producing pituitary adenoma. Ectopic ACTH secretion occurs when a non-pituitary tumor produces ACTH, leading to Cushing's syndrome. McCune-Albright syndrome is a rare genetic disorder that can cause various endocrine abnormalities, but it is not a common cause of Cushing's disease.

Correct Answer: B

Rationale: Hemoglobin A1c, also known as HbA1c or glycated hemoglobin, is a blood test that measures the average blood glucose level over the previous 2 to 3 months. This test is useful in monitoring long-term blood glucose control in individuals with diabetes. Hemoglobin A1c provides an indication of how well blood glucose levels have been controlled over time, reflecting the average blood sugar levels during the lifespan of red blood cells, which is typically around 2 to 3 months. A higher Hemoglobin A1c level indicates poorer blood glucose control and an increased risk of diabetes complications.

Correct Answer: D

Rationale: Myxoedema is a severe form of hypothyroidism characterized by a range of symptoms and signs. Ascites, cerebellar ataxia, and increased incidence of pernicious anaemia are recognized features of myxoedema. However, thyroid acropachy is not a recognized feature of myxoedema. Thyroid acropachy is a condition characterized by clubbing of the fingers and toes, swelling of the hands and feet, and periosteal new bone formation, typically seen in patients with Graves' disease, which is a form of hyperthyroidism.

Correct Answer: A

Rationale: Gastroparesis is a complication of diabetes mellitus. It is a condition that affects the normal spontaneous movement of the muscles in the stomach, causing delayed emptying of food from the stomach into the small intestine. This can lead to symptoms such as nausea, vomiting, bloating, and poor appetite. Diabetes can damage the nerves that control the stomach muscles, resulting in gastroparesis. Managing blood sugar levels and following a proper diet can help in controlling the symptoms of gastroparesis in individuals with diabetes. Exophthalmos, hirsutism, and moon facies are not typically associated with complications of diabetes mellitus.

Correct Answer: D

Rationale: Persistent muscular weakness is characteristic of myxoedema, which is severe hypothyroidism. Myxoedema can lead to general weakness and fatigue, as thyroid hormones play a crucial role in controlling metabolism and energy production in the body. Other symptoms of myxoedema include cold intolerance, weight gain, dry skin, and hair loss. Conn's syndrome (hyperaldosteronism) is characterized by hypertension and low potassium levels, not persistent muscular weakness. Acromegaly is a condition resulting from excess growth hormone production, leading to enlarged body parts and metabolic changes but not specifically muscular weakness. Hyperparathyroidism is associated with high levels of parathyroid hormone, which can lead to bone weakening and calcium imbalance, but it is not typically a primary cause of muscular weakness.