What of the following statements best describes a toxic thyroid adenoma?

Correct Answer: D

Rationale: Step 1: Toxic thyroid adenoma is characterized by a benign tumor in the thyroid gland. Step 2: This tumor produces excessive amounts of thyroid hormones, particularly T3 and T4. Step 3: The tumor arises from the follicular cells of the thyroid gland. Step 4: Choice D accurately describes a toxic thyroid adenoma as a benign tumor producing excessive thyroid hormones from follicular cells. Summary: Choice A is incorrect because it describes autoimmune thyroid disease, not a toxic adenoma. Choice B is incorrect as it describes a malignant tumor, not a benign one. Choice C is incorrect as it describes thyroiditis, not a toxic adenoma.

Correct Answer: C

Rationale: Rationale: 1. GnRH directly binds to pituitary receptors. 2. GnRH specifically targets gonadotroph cells to release LH and FSH. 3. CRH and ACTH are related to stress and adrenal function, not reproductive hormones. 4. Tremor is unrelated to pituitary hormone regulation. Summary: Gonadotrophin releasing hormone (GnRH) is the correct answer as it directly stimulates the release of LH and FSH from the pituitary gland. Other choices are incorrect as they are not involved in the regulation of reproductive hormones.

Correct Answer: A

Rationale: The correct answer is A: Adrenaline. In injury to the adrenal cortex, adrenaline is least affected because it is primarily synthesized and secreted by the adrenal medulla, not the adrenal cortex. Cortisol, aldosterone, and androstenedione are hormones produced by the adrenal cortex. In adrenal cortex injury, the secretion of cortisol, aldosterone, and androstenedione would be significantly affected due to the damage to the adrenal cortex, leading to hormonal imbalance and related symptoms. Therefore, option A is the correct answer as it is not primarily secreted by the adrenal cortex and would be least affected in this scenario.

Correct Answer: C

Rationale: The correct answer is C: Bi-temporal hemianopia. Pituitary adenoma compressing the optic chiasm typically leads to bi-temporal hemianopia due to compression of the crossing fibers from the nasal visual fields. This results in loss of peripheral vision in both temporal visual fields. A: Bilateral inferior visual field deficits and B: Bilateral superior visual field deficits are less likely as they are not typical patterns associated with optic chiasm compression. D: Right homonymous hemianopia is incorrect as it is not associated with compression of the optic chiasm by a pituitary adenoma.

Correct Answer: B

Rationale: The correct answer is B: Weight loss. Hypothyroidism is characterized by an underactive thyroid gland, leading to a decreased metabolic rate. This typically results in weight gain, not weight loss. Choices A, C, and D are all associated with hypothyroidism. Loss of libido can occur due to hormonal imbalances, cardiac failure can result from the decreased metabolic rate affecting the heart, and organic psychosis can be a symptom of severe untreated hypothyroidism.

Correct Answer: C

Rationale: The correct answer is C: Ischaemic heart disease. Metabolic syndrome X consists of a cluster of conditions, including hyperlipidemia, obesity, hypertension, and insulin resistance. Ischaemic heart disease, while commonly associated with metabolic syndrome X due to the increased risk factors, is not a direct component of the syndrome itself. Therefore, it is not considered a part of metabolic syndrome X. Hyperlipidemia (A), obesity (B), and hypertension (D) are all key components of metabolic syndrome X due to their association with insulin resistance and increased risk of cardiovascular disease.

Correct Answer: A

Rationale: The correct answer is A: Acute pancreatitis. Hyperparathyroidism is not typically associated with acute pancreatitis. Hyperparathyroidism is characterized by excessive production of parathyroid hormone, leading to increased calcium levels in the blood. Nephrocalcinosis, palpable neck swelling, and pseudogout are commonly seen in hyperparathyroidism due to the effects of elevated calcium levels on the kidneys, parathyroid glands, and joints, respectively. Acute pancreatitis, on the other hand, is more commonly associated with gallstones, alcohol consumption, or certain medications, rather than hyperparathyroidism.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Tertiary hyperparathyroidism occurs due to prolonged secondary hyperparathyroidism in response to chronic renal failure. 2. In chronic renal failure, impaired kidney function leads to reduced activation of vitamin D and impaired calcium regulation. 3. Persistent hypocalcemia triggers the parathyroid glands to overproduce parathyroid hormone, leading to tertiary hyperparathyroidism. 4. Rickets (choice A) is associated with vitamin D deficiency, pseudohypoparathyroidism (choice B) is a genetic disorder, and malabsorption syndrome (choice D) affects nutrient absorption, but they are not commonly linked to tertiary hyperparathyroidism.

Correct Answer: B

Rationale: The correct answer is B: Cortisol. The adrenal cortex produces cortisol, a steroid hormone involved in stress response and metabolism. Norepinephrine (A) is produced by the adrenal medulla. 5-DHEA (C) is a precursor to sex hormones and not directly produced by the adrenal cortex. Aldosterone (D) is produced by the adrenal cortex but is involved in regulating salt and water balance, not directly related to cortisol production.