PHYS 506 Anatomy and Physiology Endocrine Mini MCQs 70 Answers 2023/24

PHYS 506 Anatomy and Physiology Endocrine Mini MCQs 70 Answers 2023/24 (14.) A 24-year-old woman presents with a slightly elevated blood pressure. She has high plasma levels of total T4, cortisol, and renin activity, but no symptoms or signs of thyrotoxicosis or Cushing syndrome. Which of the following is the most likely explanation? (A) She has been treated with ACTH and TSH. (B) She has been treated with T3 and cortisol. (C) She has an adrenocortical tumor. (D) She is in the third trimester of pregnancy (E) She has been subjected to chronic stress. Answer: D. Thyroxin-binding globulin (TBG) is increased in estrogen-treated patients and during pregnancy, increasing the total plasma levels of T3 and T4, but with a normal level of the free thyroid hormones, such that the clinical state is euthyroid. Cortisol levels also increase during pregnancy and parturition due to increased production of corticotropin-releasing hormone (CRH) by the placenta (as well as the fetal hypothalamus). Although tissue renin contributes little to the circulating renin pool, pregnancy is associated with increased renin levels that may arise from components of the tissue renin-angiotensin system found in the uterus, the placenta, and the fetal membranes. Amniotic fluid contains large amounts of prorenin. 2. (16.) Which of the following hormones acts by an inositol 1,4,5-triphosphate (IP3)-Ca2+ mechanism of action? (A) 1,25 –Dihydroxycholecalciferol (Steroid Hormone) (B) Progesterone (Steroid Hormone) (C) Insulin (Tyrosine Kinase) (D) Parathyroid hormone (PTH) (cAMP) (E) Gonadotropin-releasing hormone (GnRH) Answer: E. Gonadotropin-releasing hormone (GnRH) is a peptide hormone that acts on the cells of the anterior pituitary by an inositol 1,4,5-triphosphate (IP3)-Ca2+ mechanism to cause the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). 1,25-Dihydroxycholecalciferol and progesterone are steroid hormone derivatives of cholesterol that act by inducing the synthesis of new proteins. Insulin acts on its target cells by a tyrosine kinase mechanism. Parathyroid hormone (PTH) acts on its target cells by an adenylate cyclase-cyclic adenosine monophosphate (cAMP) mechanism. 3. (30.) As compared with the concentration of Na+ in the plasma and urine of a normal person, the Na+ in the plasma and urine of a patient with inappropriate ADH secretion (SIADH) will be: Plasma concentration of Na+ Urine concentration of Na+ (A) Below normal Below normal (B) Above normal Above normal (C) Above normal Below normal (D) Below normal Above normal (E) Normal Normal Answer: D. The excessive plasma ADH will stimulate reabsorption of water in the renal collecting duct. This will expand ECF and the blood volume, and slightly elevate blood pressure. As a result, the secretion of renin, angiotensin II, and aldosterone will decrease. The decrease in aldosterone decreases renal Na+ reabsorption. Urine Na+ concentration increases, while plasma Na+ concentration decreases. 4. (33.) In the following figure, which lines most likely reflect the responses in a patient with nephrogenic diabetes insipidus? (A) A and C (B) A and D (C) B and C (D) B and D Answer: B. In patients with nephrogenic diabetes insipidus, the kidneys do not respond appropriately to antidiuretic hormone (ADH), and the ability to form concentrated urine is impaired. In contrast, there is a normal ADH secretory response to changes in plasma osmolality. 5. (36.) A 55-year-old man has developed the syndrome of inappropriate antidiuretic hormone secretion due to carcinoma of the lung. Which of the following physiological responses would be expected? (A) Increased plasma osmolality (B) Inappropriately low urine osmolality (relative to plasma osmolality) (C) Increased thirst (D) Decreased secretion of antidiuretic hormone from the pituitary gland Answer: D. An inappropriately high rate of antidiuretic hormone (ADH) secretion from the lung promotes excess water reabsorption, which tends to produce concentrated urine and a decrease in plasma osmolality. Low plasma osmolality suppresses both thirst and ADH secretion from the pituitary gland. 6. (50.) Which one of the following statements correctly compares the effects of removal of the anterior pituitary (hypophysectomy) with the effects of removal of the adrenal glands (adrenalectomy)? (A) The capacity to withstand a fast will be decreased following hypophysectomy, but not following adrenalectomy. (B) The daily rate of urinary excretion of 17-hydroxy steroids will be decreased following adrenalectomy, but not following hypophysectomy. (C) The daily rate of urinary excretion of 17-keto steroids will be decreased following hypophysectomy, but not following adrenalectomy. (D) The plasma glucose concentration will be elevated following hypophysectomy, but not following adrenalectomy. (E) A marked loss of Na+ from the extracellular fluid occurs following adrenalectomy, but not following hypophysectomy. Answer: E. Following adrenalectomy, but not following hypophysectomy, secretion of the mineralocorticoid aldosterone is absent. Loss of aldosterone results in excessive Na+ excretion accompanied by loss of ECF volume, the net effect often being fatal hypotension. Regarding choices A and D, both adrenalectomy and hypophysectomy will abolish (or greatly lower) the plasma glucocorticoid (cortisol) and adrenal sex steroid concentration, resulting in decreased 17-hydroxy- and 17-ketosteroid excretion. Loss of glucocorticoid will decrease the capacity of the individual to mobilize energy stores during a fast, and the diminished rate of liver gluconeogenesis will lower blood glucose. 7. (64.) Which of the following inhibits the secretion of growth hormone by the anterior pituitary? (A) Sleep (B) Stress (C) Puberty (D) Somatomedins (E) Starvation (F) Hypoglycemia Answer: D. Growth hormone is secreted in pulsatile fashion, with a large burst occurring during deep sleep (sleep stage 3 or 4). Growth hormone secretion is increased by sleep, stress, puberty, starvation, and hypoglycemia. Somatomedins are generated when growth hormone acts on its target tissues; they inhibit growth hormone secretion by the anterior pituitary both directly and indirectly (by stimulating somatostatin release). 8. (66.) Which of the following sets of physiological changes would be most likely to occur in a patient with acromegaly? Pituitary mass Kidney mass Femur length (A) ↓ ↓ ↑ (B) ↓ ↑ ↑ (C) ↑ ↔ ↔ (D) ↑ ↑ ↔ (E) ↑ ↑ ↑ Answer: D. A pituitary tumor secreting growth hormone is likely to present as an increase in pituitary gland size. The anabolic effects of excess growth hormone secretion lead to enlargement of the internal organs, including the kidneys. Because acromegaly is the state of excess growth hormone secretion after epiphyseal closure, increased femur length dues not occur. 9. (71.) Which of the following sets of physiological changes is most likely to occur in a patient in the early stages of acromegaly? Somatomedin C Production Somatostatin Secretion Insulin Secretion (A) ↑ ↓ ↔ (B) ↑ ↑ ↓ (C) ↑ ↑ ↑ (D) ↓ ↓ ↔ (E) ↓ ↑ ↑ Answer: C. The adult form of excess growth hormone secretion is called acromegaly and is usually associated with a pituitary tumor. Increased plasma levels of growth hormone stimulate the liver and other tissues to produce somatomedin C. As a result of feedback, increased plasma levels of somatomedin C cause the hypothalamus to increase the secretion of growth hormone–inhibiting hormone, somatostatin. Elevated plasma levels of growth hormone also tend to increase plasma glucose concentration, which favors an increase in insulin secretion. . . . . . .. . . . . .