Thyrotoxicosis may be featured by all except:

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: 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: In Cushing's syndrome, the adrenal glands produce an excess amount of cortisol over an extended period. The correct answer is C) Sexual precocity. This option is not typically associated with Cushing's syndrome. Here's why the other options are incorrect: A) Psychosis: Patients with Cushing's syndrome can experience psychological symptoms like depression, anxiety, and mood changes, but psychosis is not a typical feature. B) Systemic hypertension: Hypertension is a common feature of Cushing's syndrome due to the effects of excess cortisol on blood pressure regulation. D) Osteoporosis: Excess cortisol can lead to bone loss and osteoporosis in Cushing's syndrome due to its negative effects on bone density. Educational context: Understanding the signs and symptoms of Cushing's syndrome is crucial for healthcare professionals in diagnosing and managing this condition. By knowing the typical manifestations, such as hypertension, osteoporosis, and psychological symptoms, clinicians can promptly identify and treat patients with Cushing's syndrome. Recognizing atypical features like sexual precocity can also aid in ruling out other conditions.

Correct Answer: A

Rationale: Congenital adrenal hyperplasia does not lead to dwarfism. It is a group of genetic disorders that affect the adrenal glands and can cause various symptoms related to hormone imbalances. In contrast, the other conditions listed - hypopituitarism, homocystinuria, and pseudohypoparathyroidism - can all lead to dwarfism through different mechanisms. Hypopituitarism is characterized by a deficiency of pituitary hormones, including growth hormone, which can result in stunted growth and dwarfism. Homocystinuria is a metabolic disorder that can affect bone growth and lead to skeletal abnormalities resulting in dwarfism. Pseudohypoparathyroidism is a rare genetic disorder that can manifest with short stature or dwarfism due to skeletal abnormalities caused by altered bone metabolism.