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: D

Rationale: Neurogenic diabetes insipidus is due to a deficiency in vasopressin (antidiuretic hormone, ADH) production in the hypothalamus or a failure of proper vasopressin release from the posterior pituitary. Causes of neurogenic DI typically involve factors affecting vasopressin synthesis, storage, or release. However, mutations in the vasopressin gene itself would be a cause of genetic forms of diabetes insipidus, not neurogenic diabetes insipidus. Common causes of neurogenic diabetes insipidus include traumatic brain injury, brain tumors, pituitary adenomas, meningitis, and Sheehan's syndrome.

Correct Answer: C

Rationale: Growth hormone deficiency (GHD) is commonly associated with decreased bone mineral density, leading to an increased risk of fractures and osteoporosis. Therefore, increased bone mineral density would not typically be a sign or symptom of GHD. On the other hand, abnormal lipid profile, atherosclerosis, and left ventricular dysfunction are all potential signs or symptoms of GHD. Abnormal lipid profile can manifest as increased levels of LDL cholesterol and decreased levels of HDL cholesterol. Atherosclerosis, the buildup of plaque in the arteries, can occur in individuals with GHD due to the impact on lipid metabolism. Left ventricular dysfunction may also be seen in individuals with GHD due to the role of growth hormone in cardiac function and structure.

Correct Answer: A

Rationale: Acromegaly is a hormonal disorder that results from the overproduction of growth hormone (GH) in adulthood. One of the key physical characteristics associated with acromegaly is the enlargement of facial features. People with acromegaly often develop prognathism, which is a condition where the lower jaw protrudes forward, leading to a prominent lower face. Additionally, they may have large fleshy lips due to the soft tissue swelling that occurs as a result of excess GH. Other common signs of acromegaly include enlarged hands and feet, thickened skin, and joint pain.

Correct Answer: B

Rationale: In males, Leydig cells in the testes are stimulated to produce testosterone by luteinizing hormone (LH). LH is produced by the anterior pituitary gland and acts on the Leydig cells to promote the synthesis and release of testosterone. This hormone plays a crucial role in male reproductive function and the development of masculine characteristics. Follicle stimulating hormone (FSH) plays a role in spermatogenesis in males but does not directly stimulate Leydig cells to produce testosterone.

Correct Answer: B

Rationale: The triad of hyponatremia (low sodium levels in the blood), haemodilution (increased plasma volume), and urine hypertonic to plasma (high urine osmolality compared to blood osmolality) is characteristic of Syndrome of Inappropriate Antidiuretic Hormone (SIADH). In SIADH, there is excessive release of antidiuretic hormone (ADH), also known as vasopressin, leading to water retention by the kidneys and dilutional hyponatremia. This condition results in the body holding onto water, causing hyponatremia and dilution of the blood. The urine being hypertonic compared to plasma indicates that the kidneys are reabsorbing water effectively and concentrating the urine.

Correct Answer: A

Rationale: Thyrotoxicosis, also known as hyperthyroidism, is a condition characterized by excessive thyroid hormone production by the thyroid gland. Symptoms of thyrotoxicosis can include weight loss, heat intolerance, tremors, hyperactivity, and fatigue. While musculoskeletal symptoms such as weakness and tremors are common in thyrotoxicosis, true myopathy (muscle disease) is not a typical feature of the condition. Therefore, myopathy is the correct choice among the given options.

Correct Answer: A

Rationale: Cushing's syndrome is a condition characterized by excessive levels of cortisol in the body. Cortisol is a hormone produced by the adrenal glands that helps regulate various bodily functions, including metabolism, immune response, and stress response. When there is an overproduction of cortisol, either due to excessive production by the adrenal glands or prolonged use of corticosteroid medications, it can result in Cushing's syndrome. Symptoms of Cushing's syndrome include weight gain, particularly in the face and abdomen, high blood pressure, muscle weakness, and irregularities in menstruation. It is important to diagnose and manage Cushing's syndrome to prevent potential complications such as diabetes, osteoporosis, and cardiovascular disease.

Correct Answer: A

Rationale: Hyperthermia is not a typical feature of diabetic ketoacidosis (DKA). DKA is typically characterized by high blood sugar levels, ketone accumulation, metabolic acidosis, dehydration, drowsiness, and, in severe cases, unconsciousness. Common symptoms include drowsiness, dehydration, and air hunger (deep and rapid breathing). However, hyperthermia, which refers to an elevated body temperature, is not a characteristic typically associated with DKA. It is important to monitor and manage DKA promptly as it is a serious complication of diabetes that requires immediate medical attention.