Which one of the following hormones binds to the pituitary and stimulates the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH)?

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: C

Rationale: The correct answer is C because dipsogenic diabetes insipidus is caused by a defect or damage to the hypothalamus, not the pituitary gland or pituitary stalk. The hypothalamus regulates thirst and water intake, so damage to this area can lead to excessive thirst and dilute urine output characteristic of diabetes insipidus. Choices A and D incorrectly attribute the cause to the pituitary gland or pituitary stalk, which are not directly involved in regulating thirst. Choice B is incorrect as it mentions malfunction of the hunger mechanism, which is not relevant to dipsogenic diabetes insipidus. Thus, choice C is the most accurate definition based on the pathophysiology of the condition.

Correct Answer: B

Rationale: The correct answer is B: Chronic pancreatitis. Hypoglycemia is not typically associated with chronic pancreatitis as it is more related to pancreatic insufficiency and impaired glucose regulation. A: Glycogen storage disease can lead to hypoglycemia due to the inability to properly release stored glucose. C: Galactosaemia can cause hypoglycemia due to the impaired breakdown of galactose into glucose. D: Post-gastrectomy can lead to hypoglycemia due to rapid glucose absorption and altered hormonal responses.

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: D

Rationale: The correct answer is D because oxytocin and anti-diuretic hormone are synthesized in the hypothalamus and stored in the posterior pituitary gland before being released into the bloodstream. This process is essential for regulating various physiological functions. Choices A and C are incorrect as oxytocin and anti-diuretic hormone are not complex steroids and are not released from the anterior pituitary. Choice B is also incorrect because while these hormones are indeed synthesized in the posterior pituitary, they are stored in the posterior pituitary before their release.

Correct Answer: B

Rationale: The correct answer is B: Dry skin. In hypothyroidism, the thyroid gland does not produce enough thyroid hormone, leading to decreased metabolism. This can result in several symptoms, including dry skin due to reduced sweat gland activity. Hyporeflexia (A) is not a common symptom of hypothyroidism. Oily skin (C) is more commonly associated with hyperthyroidism, where thyroid hormone levels are elevated. Excessive hair growth (D) is not typically seen in hypothyroidism; instead, hair loss is a common symptom.

Correct Answer: A

Rationale: The correct answer is A because Klinefelter's syndrome is characterized by small, soft testes due to the presence of an extra X chromosome (47, XXY). This leads to hypogonadism and inadequate testosterone production, resulting in underdeveloped testes. Choice B (46, XO) is incorrect as it refers to Turner syndrome. Choice C (upper segment> lower segment) is unrelated to Klinefelter's syndrome. Choice D (Gynaecomastia) is a symptom of Klinefelter's syndrome but not the defining characteristic.

Correct Answer: A

Rationale: Rationale: A: Correct. Cushing's disease is caused by a pituitary adenoma secreting excess ACTH, stimulating adrenal cortex to produce excess cortisol. B: Incorrect. Cushing's disease does not result from excess cortisol secretion by the pituitary adenoma. C: Incorrect. Cushing's disease is not caused by an adrenal adenoma secreting excess ACTH. D: Incorrect. Cushing's disease is not caused by an adrenal adenoma secreting excess cortisol. Summary: The correct answer is A because it accurately describes the pathophysiology of Cushing's disease, where a pituitary adenoma secretes excess ACTH leading to increased cortisol production. Choices B, C, and D are incorrect as they misinterpret the primary source of hormone overproduction in Cushing's disease.

Correct Answer: B

Rationale: The correct answer is B: Cretinism. Cretinism is the most common cause of preventable mental deficiency worldwide due to severe iodine deficiency during pregnancy. Iodine is crucial for thyroid hormone production, which is essential for fetal brain development. Beriberi disease (A) is caused by thiamine deficiency and affects the nervous system, not mental deficiency. Folate deficiency (C) can cause neural tube defects but not mental deficiency. Vitamin A deficiency (D) can lead to blindness and immune system issues, but not the most common cause of preventable mental deficiency.