Nokea
Which of the following tests should be used to make the diagnosis of Cushing's syndrome?
- A. 24-hour urine free cortisol
- B. Corticotropin-releasing hormone (CRH) level at 8 a.m.
- C. Inferior petrosal venous sampling
- D. Overnight 1-mg dexamethasone suppression test
Correct Answer: D
Rationale: The overnight 1-mg dexamethasone suppression test is commonly used as an initial screening test for Cushing's syndrome. In this test, a patient takes 1 mg of dexamethasone orally at 11 p.m., and their serum cortisol level is measured the next morning. In patients with Cushing's syndrome, the cortisol levels will not be suppressed by the dexamethasone due to the presence of excessive cortisol production.
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Which of the following is the most potent stimulus for hypothalamic production of arginine vasopressin?
- A. Hypertonicity
- B. Hyperkalemia
- C. Hypokalemia
- D. Hypotonicity
Correct Answer: A
Rationale: Hypertonicity (increased osmolarity or high concentration of solutes in the blood) is the most potent stimulus for the hypothalamic production of arginine vasopressin (also known as antidiuretic hormone or ADH). When the body senses increased plasma osmolality, the osmoreceptors in the hypothalamus stimulate the release of vasopressin from the posterior pituitary gland. Vasopressin acts on the kidneys to increase water reabsorption and decrease urine output, helping to restore normal osmolarity. This mechanism helps to conserve water and maintain body fluid balance in response to dehydration or increased solute concentration in the blood.
Acromegaly is associated with all of the following except:
- A. Acanthosis nigricans
- B. Fibromata mollusca
- C. Micrognathia
- D. Cardiomegaly
Correct Answer: C
Rationale: Acromegaly is a disorder caused by excessive growth hormone production after the closure of the epiphyses (growth plates) in bones, leading to abnormal growth of tissues and organs. The following options are associated with acromegaly:
Calcification of basal ganglia is seen in:
- A. Primary hyperparathyroidism
- B. Hypoparathyroidism
- C. Secondary hyperparathyroidism
- D. Milk-alkali syndrome
Correct Answer: A
Rationale: Primary hyperparathyroidism is a condition characterized by the overproduction of parathyroid hormone (PTH) by the parathyroid glands, leading to elevated levels of calcium in the blood. This excessive calcium can cause calcification in various tissues, including the basal ganglia of the brain. The calcification of the basal ganglia in primary hyperparathyroidism is a well-known radiological finding and can be visualized on imaging studies such as CT scans or MRI. Hypoparathyroidism, on the other hand, is characterized by low levels of PTH and results in decreased serum calcium levels, making it an unlikely cause of basal ganglia calcification. Secondary hyperparathyroidism is associated with chronic kidney disease and is also characterized by high PTH levels, but basal ganglia calcification is not a typical manifestation of this condition. Milk-alkali syndrome is a disorder characterized by excessive intake of
Oxytocin and antidiuretic hormone (ADH; vasopressin) are:
- A. complex steroids.
- B. synthesized and stored in the posterior pituitary.
- C. released from the anterior pituitary where blood is hypotonic.
- D. synthesized in the hypothalamus and released from the posterior pituitary.
Correct Answer: D
Rationale: Oxytocin and antidiuretic hormone (ADH; vasopressin) are both synthesized in the hypothalamus, specifically in the supraoptic and paraventricular nuclei. After synthesis, they are transported along axons to the posterior pituitary where they are stored until they are released into the bloodstream when needed. This is why they are released from the posterior pituitary, not the anterior pituitary. These hormones have different functions in the body, with oxytocin being involved in labor and breastfeeding, while ADH plays a role in regulating water balance and blood pressure.
In males which hormone stimulates Leydig cells to produce testosterone?
- A. Follicle stimulating hormone (FSH)
- B. Luteinizing hormone (LH)
- C. hormone
- D. insipidus
Correct Answer: B
Rationale: In males, Leydig cells in the testes are stimulated to produce testosterone by luteinizing hormone (LH). LH is produced by the anterior pituitary gland and acts on the Leydig cells to promote the synthesis and release of testosterone. This hormone plays a crucial role in male reproductive function and the development of masculine characteristics. Follicle stimulating hormone (FSH) plays a role in spermatogenesis in males but does not directly stimulate Leydig cells to produce testosterone.