Which of the following is the most common cause of hypothyroidism worldwide?

Correct Answer: D

Rationale: Iodine deficiency is the most common cause of hypothyroidism worldwide. Iodine is an essential mineral required for the production of thyroid hormones. Without sufficient iodine, the thyroid gland is unable to produce an adequate amount of thyroid hormones, leading to hypothyroidism. Areas with low iodine levels in the soil or water are more prone to iodine deficiency, which can result in a range of thyroid disorders, including hypothyroidism. Efforts to prevent iodine deficiency include iodized salt programs and dietary interventions to ensure an adequate intake of iodine.

Correct Answer: A

Rationale: Cirrhosis is not a potential cause of elevated LDL cholesterol levels. The liver plays a significant role in cholesterol metabolism, and liver disease like cirrhosis can actually lead to decreased levels of LDL cholesterol. Elevated LDL cholesterol levels can be caused by conditions such as hypothyroidism, nephrotic syndrome, or the use of certain medications like thiazide diuretics.

Correct Answer: A

Rationale: Thyroid-stimulating hormone (TSH) is a glycoprotein hormone that is produced and secreted by the anterior pituitary gland. It acts on the thyroid gland to stimulate the production and release of thyroid hormones, T3 (triiodothyronine) and T4 (thyroxine). TSH plays a crucial role in regulating the function of the thyroid gland and maintaining overall thyroid hormone levels in the body.

Correct Answer: A

Rationale: Acromegaly is a disorder caused by excessive growth hormone production by the pituitary gland in adults, leading to an increase in muscle mass (hypertrophy). Hoffman syndrome, characterized by increased muscle mass with slowness of activity, is a clinical feature often seen in individuals with acromegaly. The excessive growth hormone levels in acromegaly can cause acral growth, soft tissue swelling, and muscle hypertrophy, contributing to the characteristic features of the condition, including Hoffman syndrome. Therefore, the correct answer is Acromegaly.

Correct Answer: A

Rationale: Centripetal obesity, acne, and hirsutism are classic features of Cushing's syndrome. Cushing's syndrome results from prolonged exposure to high levels of cortisol, which can be due to various causes such as adrenal tumors, pituitary adenomas, or exogenous glucocorticoid use. Centripetal obesity refers to the characteristic fat distribution pattern seen in Cushing's syndrome, where fat accumulates mainly in the face, neck, and trunk while sparing the limbs. Acne and hirsutism are also commonly seen in Cushing's syndrome due to the hormonal imbalances caused by excess cortisol. Testing for serum cortisol levels, dexamethasone suppression tests, and imaging studies can help confirm the diagnosis of Cushing's syndrome in a patient presenting with these symptoms.

Correct Answer: A

Rationale: Pseudo-Cushing's syndrome is a condition that mimics the symptoms of Cushing's syndrome but is not actually caused by excess cortisol production by the adrenal glands. It can be caused by various conditions such as chronic alcoholism, obesity, depression, and certain medications. However, myxoedema (also known as severe hypothyroidism) is not typically associated with pseudo-Cushing's syndrome. Myxoedema is characterized by low thyroid hormone levels, which would not lead to the symptoms of pseudo-Cushing's syndrome.

Correct Answer: B

Rationale: Nephrogenic diabetes insipidus (NDI) is a condition where the kidneys are unable to respond to antidiuretic hormone (ADH) as they should, leading to excessive urination and extreme thirst. One of the main causes of nephrogenic diabetes insipidus is the use of certain medications, with lithium being the most common culprit. Lithium can interfere with the kidney's response to ADH, resulting in decreased water reabsorption and the characteristic symptoms of diabetes insipidus. Other causes of NDI can include genetic mutations affecting the vasopressin receptor gene or other underlying conditions such as hypercalcemia, hypokalemia, or obstructive uropathy.

Correct Answer: A

Rationale: Acromegaly most commonly affects individuals in the age group of 30-50 years. This condition is typically diagnosed in adults between these ages. Acromegaly is often caused by the overproduction of growth hormone in adults, which leads to excessive bone growth and tissue expansion. While acromegaly can develop at any age, it is more commonly seen in adults within the 30-50 age range.

Correct Answer: B

Rationale: Conn's syndrome, also known as primary hyperaldosteronism, is characterized by excess production of aldosterone by the adrenal glands. This leads to increased sodium retention and potassium excretion in the kidneys. As a result, patients with Conn's syndrome typically present with hypokalemia (low potassium levels), not hyperkalemia (high potassium levels). The other features of Conn's syndrome include alkalosis (metabolic), muscle cramps, and severe systemic hypertension.