Hypocalcemia is produced by all except:

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: A

Rationale: Dermal hyperpigmentation, also known as hyperpigmentation of the skin, is commonly associated with conditions such as Addison's disease, hemochromatosis, and bronchogenic carcinoma. In Addison's disease, there is increased production of melanin due to elevated levels of adrenocorticotropic hormone (ACTH) which stimulates melanocytes. Hemochromatosis can cause hyperpigmentation due to excess iron deposits in the skin. Bronchogenic carcinoma can lead to a condition known as acanthosis nigricans, characterized by dark, velvety discoloration of the skin primarily around the neck and armpits. However, Conn's syndrome, which is a primary aldosteronism resulting from an adrenal adenoma or hyperplasia, is not typically associated with dermal hyperpigmentation.

Correct Answer: D

Rationale: Medullary carcinoma of the thyroid typically presents with symptoms related to the thyroid gland itself, neck mass or swelling, and sometimes cervical lymphadenopathy. It is characterized by the production of calcitonin, leading to high serum calcitonin levels. Carcinoid syndrome, which includes symptoms such as flushing, diarrhea, and wheezing, is more commonly associated with neuroendocrine tumors, rather than medullary carcinoma of the thyroid. Psychosis is not a typical feature or manifestation of medullary carcinoma of the thyroid.

Correct Answer: A

Rationale: Phaeochromocytoma is a neuroendocrine tumor that arises from the chromaffin cells of the adrenal medulla. It is the most common cause of a catecholamine-secreting tumor in adults. While it can also rarely occur outside the adrenal gland (referred to as extra-adrenal or paraganglioma), the majority of cases originate within the adrenal medulla. Symptoms of phaeochromocytoma are due to the excessive release of catecholamines (epinephrine and norepinephrine), leading to a characteristic triad of headaches, sweating, and palpitations. Therefore, the commonest cause of phaeochromocytoma is a tumor of the adrenal medulla.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.