Nokea
Oxytocin:
- A. is bound to neurophysin in plasma.
- B. inhibits production of milk.
- C. inhibits myometrial contraction.
- D. inhibits sperm swimming on the gonad.
Correct Answer: A
Rationale: Oxytocin is a hormone produced by the hypothalamus and released by the pituitary gland. In the bloodstream, oxytocin is mostly bound to a carrier protein called neurophysin. This binding helps to protect oxytocin from being degraded too quickly in the bloodstream, thus allowing it to exert its effects on target tissues such as the uterus and mammary glands. Oxytocin plays important roles in stimulating uterine contractions during labor, facilitating milk letdown during breastfeeding, and promoting social bonding and emotional connections.
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Which of the following are causes of nephrogenic diabetes insipidus?
- A. Sheehan's syndrome
- B. Lithium
- C. Mutations in the vasopressin (ADH) receptor gene
- D. Mutations in vasopressin gene
Correct Answer: B
Rationale: Nephrogenic diabetes insipidus (NDI) is a condition where the kidneys are unable to respond to antidiuretic hormone (ADH) as they should, leading to excessive urination and extreme thirst. One of the main causes of nephrogenic diabetes insipidus is the use of certain medications, with lithium being the most common culprit. Lithium can interfere with the kidney's response to ADH, resulting in decreased water reabsorption and the characteristic symptoms of diabetes insipidus. Other causes of NDI can include genetic mutations affecting the vasopressin receptor gene or other underlying conditions such as hypercalcemia, hypokalemia, or obstructive uropathy.
What is the most common cause of Cushing's syndrome?
- A. Ectopic ACTH production
- B. Adrenal adenoma
- C. Glucocorticoid treatment (iatrogenic)
- D. Pituitary adenoma
Correct Answer: D
Rationale: The most common cause of Cushing's syndrome is a pituitary adenoma, specifically a corticotroph adenoma. This adenoma leads to excessive secretion of adrenocorticotropic hormone (ACTH) by the pituitary gland, which in turn stimulates the adrenal glands to produce high levels of cortisol. This results in the symptoms and signs characteristic of Cushing's syndrome. Pituitary adenomas are responsible for around 70-80% of cases of Cushing's syndrome, making it the most common cause.
Which of the following are causes of Addison's disease?
- A. Adrenoleukodystrophy
- B. Pyelonephritis
- C. Tuberculosis
- D. Autoimmune destruction of the adrenal cortex
Correct Answer: D
Rationale: Addison's disease, also known as primary adrenal insufficiency, is mainly caused by the autoimmune destruction of the adrenal cortex. This results in the inadequate production of hormones such as cortisol and aldosterone by the adrenal glands. While other conditions such as Adrenoleukodystrophy, Pyelonephritis, and Tuberculosis can also affect the adrenal glands, they are not known to be direct causes of Addison's disease.
Vanillylmandelic acid (VMA) excretion is increased in urine in:
- A. Conn's syndrome
- B. Congenital adrenal hyperplasia
- C. Testicular feminization syndrome
- D. Phaeochromocytoma
Correct Answer: D
Rationale: Vanillylmandelic acid (VMA) is a metabolite of catecholamines, such as epinephrine and norepinephrine. Phaeochromocytoma is a catecholamine-secreting tumor that arises from the chromaffin cells in the adrenal medulla or sympathetic ganglia. As a result of the increased production of catecholamines in patients with phaeochromocytoma, there is an increase in VMA excretion in the urine. This increase in VMA excretion is a significant diagnostic feature of phaeochromocytoma and helps in its detection through urine testing. Therefore, the correct choice is D. Phaeochromocytoma.
All the following drugs are associated with an increased risk of osteoporosis in adults except:
- A. Cyclosporine
- B. Heparin
- C. Prednisone
- D. Ranitidine
Correct Answer: D
Rationale: Ranitidine is not associated with an increased risk of osteoporosis in adults. It is a histamine-2 blocker commonly used to reduce stomach acid production and treat conditions such as ulcers and gastroesophageal reflux disease. On the other hand, the other options listed are known to increase the risk of osteoporosis: