Which of the following lung cancers is most commonly associated with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)?

Correct Answer: B

Rationale: Small cell (oat cell) carcinoma of the lung is most commonly associated with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). This paraneoplastic syndrome occurs in patients with small cell lung cancer due to the production of antidiuretic hormone (ADH) by the tumor cells. The excessive release of ADH leads to water retention and dilutional hyponatremia, causing symptoms such as nausea, confusion, seizures, and potentially life-threatening complications. Other types of lung cancer, such as squamous cell carcinoma, large cell carcinoma, and adenocarcinoma, are less commonly associated with SIADH.

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: 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: B

Rationale: Primary hyperaldosteronism, also known as Conn's syndrome, is characterized by excessive production of aldosterone by the adrenal glands, leading to increased sodium reabsorption and potassium excretion in the kidneys. The typical features of primary hyperaldosteronism include hypertension (often systolic), hypokalemia, metabolic alkalosis, and oedema due to sodium retention. Paraesthesia, which refers to abnormal sensations such as tingling or numbness, is not a common feature associated with primary hyperaldosteronism.

Correct Answer: C

Rationale: Tetany is a condition characterized by involuntary muscle spasms and contractions due to low levels of calcium in the blood. The signs associated with tetany include Trousseau's sign, which is the carpal spasm elicited by inflating a blood pressure cuff above systolic pressure, and Chvostek's sign, which is the facial muscle spasm elicited by tapping on the facial nerve. Peroneal sign is not specifically associated with tetany but can be seen in conditions like peroneal nerve injury. Erb's sign, on the other hand, is not a recognized sign of tetany. It is associated with Erb's palsy, a condition resulting from injury to the brachial plexus nerves, typically during childbirth. Tinel's sign, which is a tingling sensation elicited by tapping over a compressed nerve, is also not a characteristic sign of tetany.