Endocrinology Practice Questions

Correct Answer: C

Rationale: The correct answer is C: SIADH. Secondary hyperaldosteronism is characterized by increased aldosterone production due to factors outside of the adrenal glands, such as increased renin-angiotensin-aldosterone system activation. SIADH does not involve aldosterone, but rather involves inappropriate secretion of antidiuretic hormone leading to hyponatremia. In contrast, congestive cardiac failure, nephrotic syndrome, and cirrhosis of the liver can all lead to secondary hyperaldosteronism due to mechanisms such as decreased effective circulating volume, renal hypoperfusion, and increased angiotensin II levels, respectively.

Correct Answer: B

Rationale: Thyroid acropathy, also known as thyroid dermopathy, is a skin condition commonly associated with Graves' disease. This autoimmune disorder causes an overactive thyroid gland, leading to high levels of thyroid hormones in the blood. The excess thyroid hormones can trigger changes in the skin, resulting in thyroid acropathy. Subclinical hypothyroidism (choice A) is characterized by slightly elevated TSH levels with normal thyroid hormone levels, not typically associated with thyroid acropathy. Myxoedema (choice C) refers to severe hypothyroidism and is not linked to thyroid acropathy. Medullary carcinoma of the thyroid (choice D) is a type of thyroid cancer and is not known to cause thyroid acropathy. Therefore, the correct answer is B, Graves' disease, as it is the most common condition associated with thyroid acropathy.

Correct Answer: B

Rationale: The correct answer is B: Kidney disease. Oral contraceptive pills are contraindicated in patients with kidney disease due to the risk of impaired drug clearance and potential adverse effects on renal function. Breast cancer (A), liver disease (C), and prior history of deep venous thrombosis (D) are all contraindications to the use of oral contraceptives due to increased risks of complications such as thrombosis or exacerbation of underlying conditions.

Correct Answer: A

Rationale: Step-by-step rationale for why answer A is correct: 1. Oxytocin is synthesized in the hypothalamus and released into the bloodstream. 2. In the plasma, oxytocin binds to neurophysin, a carrier protein. 3. This binding helps stabilize oxytocin and regulate its release and distribution. 4. Therefore, choice A is correct as oxytocin is bound to neurophysin in plasma. Summary: - Choice B is incorrect as oxytocin stimulates milk ejection, not inhibits milk production. - Choice C is incorrect as oxytocin promotes myometrial contraction during labor. - Choice D is incorrect as oxytocin can enhance sperm motility, not inhibit it.

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.