Nokea
Which one of the following statements describes the underlying pathology of Grave's disease?
- A. An autoimmune disease directed against thyroid stimulating hormone (TSH) receptors. The autoantibodies stimulate the TSH receptors causing increased T3 and T4 production.
- B. Inflammation of the thyroid gland due to lymphocytic infiltration causes the stored thyroid hormones to be released into the circulation leading to hyperthyroidism.
- C. Consumption of ground beef which has been contaminated with thyroid tissue. The thyroid tissue contains metabolically active thyroid hormones which causes hyperthyroidism.
- D. A benign tumour of the thyroid gland which produces excessive amounts of thyroid hormones.
Correct Answer: A
Rationale: Graves' disease is an autoimmune disorder where autoantibodies, known as thyroid-stimulating immunoglobulins (TSIs) or thyroid-stimulating antibodies (TSAs), bind to and stimulate the thyroid-stimulating hormone (TSH) receptors on thyroid follicular cells. This leads to increased production and secretion of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), causing hyperthyroidism. The autoantibodies essentially mimic the action of TSH, resulting in excess thyroid hormone release and manifestation of hyperthyroid symptoms. This underlying pathology of Graves' disease is distinct from other causes of hyperthyroidism, making choice A the correct statement.
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Sheehan's syndrome presents with:
- A. Cardiac failure
- B. Persistent lactation
- C. Fever
- D. Striking cachexia
Correct Answer: B
Rationale: Sheehan's syndrome, also known as postpartum hypopituitarism, is a condition characterized by pituitary gland dysfunction due to severe blood loss during childbirth, resulting in ischemic necrosis of the pituitary gland. As a consequence of pituitary hormone deficiency, one of the hallmark manifestations of Sheehan's syndrome is persistent lactation despite stopping breastfeeding. This occurs due to inadequate prolactin inhibition, leading to continuous milk production. Other common symptoms of Sheehan's syndrome include fatigue, weight loss, menstrual irregularities, hypothyroidism, adrenal insufficiency, and other pituitary hormone deficiencies. Cardiac failure, fever, and striking cachexia are not typical presentations associated with Sheehan's syndrome.
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.
Which one of the following statements best describes an Addisonian crisis?
- A. Severe adrenal insufficiency resulting in dangerously low serum testosterone levels
- B. Dangerously high levels of testosterone
- C. Dangerously high serum cortisol levels
- D. Severe adrenal insufficiency resulting in dangerously low serum cortisol levels
Correct Answer: D
Rationale: An Addisonian crisis, also known as an acute adrenal crisis, is a life-threatening medical emergency that occurs due to severe adrenal insufficiency, leading to a sudden drop in cortisol levels. Cortisol is a vital hormone produced by the adrenal glands, and its deficiency can result in serious symptoms such as hypotension, dehydration, electrolyte imbalances, and shock. If left untreated, an Addisonian crisis can be fatal. Therefore, the correct description of an Addisonian crisis is severe adrenal insufficiency resulting in dangerously low serum cortisol levels.
Oxytocin:
- A. is not produced in males.
- B. inhibits lactation.
- C. stimulates smooth muscle contraction.
- D. is produced primarily in the SON in the hypothalamus.
Correct Answer: C
Rationale: Oxytocin is a hormone that is produced in both males and females. In females, oxytocin plays a crucial role in various physiological processes, notably during labor and childbirth. Oxytocin acts on the smooth muscles of the uterus, causing them to contract during labor (parturition) and helps in the ejection of milk during breastfeeding. This hormone is primarily synthesized in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) of the hypothalamus and stored in the posterior pituitary gland before being released into the bloodstream. Overall, oxytocin's main function is to stimulate smooth muscle contraction in the uterus and the mammary glands.
Postmenopausal estrogen therapy has been shown to increase a female's risk of all the following clinical outcomes except:
- A. Breast cancer
- B. Hip fracture
- C. Myocardial infarction
- D. Venous thromboembolism Endocrine Answers 1 C 26 B 51 D 76 B 2 C 27 A 52 A 77 C 3 B 28 C 53 B 78 D 4 B 29 D 54 B 79 D 5 C 30 B 55 C 80 C 6 A 31 B 56 C 81 C 7 A 32 D 57 B 82 A 8 B 33 D 58 C 83 C 9 C 34 C 59 A 84 B 10 C 35 C 60 A 85 A 11 B 36 A 61 B 86 B 12 A 37 D 62 A 87 D 13 B 38 B 63 A 88 A 14 C 39 D 64 B 89 C 15 D 40 A 65 B 90 A 16 D 41 D 66 D 91 D 17 A 42 D 67 A 92 B 18 C 43 D 68 C 93 A 19 A 44 B 69 A 94 A 20 B 45 B 70 A 95 A 21 A 46 A 71 A 96 D 22 B 47 C 72 B 97 D 23 B 48 A 73 D 98 B 24 B 49 D 74 B 99 D 25 B 50 C 75 D 100 B
Correct Answer: B
Rationale: Postmenopausal estrogen therapy has been shown to have a protective effect on bone density and reduce the risk of osteoporosis-related fractures, including hip fractures. Estrogen therapy helps to maintain bone strength and reduce the chances of fractures in postmenopausal women. Therefore, estrogen therapy does not increase the risk of hip fractures; in fact, it may decrease the risk of hip fractures in this population.