Which of the following drugs would be most appropriate for the boy diagnosed with Laron dwarfism?

Correct Answer: C

Rationale: The correct answer is C: Mecasermin. This drug is a recombinant human insulin-like growth factor-1 (IGF-1) and is used to treat Laron dwarfism, a condition characterized by IGF-1 deficiency. Mecasermin directly targets the underlying cause of the condition by providing the necessary growth factor. A: Somatropin is recombinant human growth hormone and is not as effective in treating Laron dwarfism as it primarily targets the growth hormone pathway. B: Octreotide is a somatostatin analog used to treat conditions like acromegaly, not Laron dwarfism. D: Oxandrolone is an anabolic steroid that may help increase growth in some cases, but it does not directly address the underlying cause of Laron dwarfism like Mecasermin does.

Correct Answer: D

Rationale: The correct answer is D: Stimulation of thyroid peroxidase. In the patient's disease, a drug would likely be used to increase thyroid hormone production. Thyroid peroxidase plays a crucial role in thyroid hormone synthesis by catalyzing the iodination of tyrosine residues on thyroglobulin. By stimulating thyroid peroxidase activity, the drug can enhance thyroid hormone production. The other choices (A, B, C) are incorrect because inhibiting thyroid protease, topoisomerase I, or proteolysis of thyroglobulin would not directly impact thyroid hormone synthesis and, therefore, would not likely mediate the therapeutic effect in the patient's disease.

Correct Answer: A

Rationale: The correct answer is A: Hyponatremia. Glucocorticoids without salt-retaining activity do not cause sodium retention, leading to hyponatremia. This is due to their lack of mineralocorticoid effects. The other choices are incorrect because hypercalcemia (B) is associated with hyperparathyroidism or excessive vitamin D, hypokalemia (C) is linked to potassium-wasting diuretics or renal tubular acidosis, and hyperglycemia (D) can be caused by factors like diabetes or excessive carbohydrate intake.

Correct Answer: D

Rationale: The correct answer is D. Therapy typically suppresses the immune system, leading to a decrease in lymphocytes. Lymphocytes are a key component of the immune system, so a decrease is expected with therapy. Neutrophils are primary defenders against infections, so they would not decrease. Erythrocytes are red blood cells responsible for oxygen transport and their decrease would lead to anemia, not a typical therapy response. Basophils are involved in allergic reactions and inflammation, so an increase in basophils would not be a typical response to therapy.

Correct Answer: B

Rationale: The correct answer is B: Fludrocortisone excess. In Addison's disease, there is adrenal insufficiency leading to low levels of cortisol and aldosterone. Fludrocortisone is a synthetic mineralocorticoid used to replace aldosterone in the treatment of Addison's disease. Excess fludrocortisone can cause retention of sodium and water, leading to hypertension, hypokalemia, weakness, and paresthesias. Constipation can also occur due to altered electrolyte balance. A: Cortisol-induced hyperglycemia is not the best explanation for the patient's symptoms as hyperglycemia is not a prominent feature of Addison's disease. C: Inadequate therapy of adrenal insufficiency would not cause the specific symptoms mentioned. D: Cortisol-induced myopathy is not the primary cause of weakness and paresthesias in Addison's disease; aldosterone deficiency leading to electrolyte imbalance is more relevant.