A 54-year-old man with a history of smoking and lung cancer develops hypercalcemia. He is enrolled in a research study to assess the efficacy of a new synthetic agent to treat this condition. After several days of treatment, he reports persistent numbness and tingling around his mouth. Physical examination is significant for facial spasm when the jaw is tapped and carpal spasm when the blood pressure cuff is inflated.
Which of the following was most likely used to treat his hypercalcemia?
A. Calcitonin B. Parathyroid hormone C. Parathyroid hormone-related peptide D. Thyroxine E. Vitamin D
Calcitonin-the correct answer is a. this vignette describes a patient with classic symptoms and signs of hypocalcemia, including chvosteks sign (facial spasm) and trousseaus sign (carpal spasm). all of these findings can be attributed to the physiologic effects of calcitonin. calcitonin is normally secreted in response to elevated levels of serum calcium and causes decreased bone resorption of calcium, resulting in lower calcium levelsanswer b is incorrect. pth acts to increase serum calcium and phosphate levels by increasing bone resorption and renal reabsorption of calcium. additionally, pth-related peptide (pthrp) stimulates conversion of inactive 25-oh vitamin d to active 1,25-oh vitamin d, resulting in hypercalcemia rather than hypocalcemiaanswer c is incorrect. pthrp acts like pth to increase serum calcium and phosphate levels by increasing bone resorption and renal reabsorption of calcium. additionally, pthrp stimulates conversion of inactive 25-oh vitamin d to active 1,25-oh vitamin d, resulting in hypercalcemia rather than hypocalcemia. metastatic small cell lung cancer can plausibly account for a nodule palpable in the neck and is generally associated with paraneoplastichypercalcemia secondary to elaboration of pthrpanswer d is incorrect. thyroxine is generally not known to significantly affect serum calcium levels. therefore, excess thyroxine would not be expected to cause hypocalcemia. the functions of thyroxine are summarized by the 4 bs: brain maturation, bone growth, -adrenergic effects, and increase basal metabolic rateanswer e is incorrect. vitamin d stimulates calcium and phosphate absorption from the intestines and increases bone resorption, resulting in increased serum calcium and phosphate levels. hence, excess vitamin d would result in hypercalcemia rather than hypocalcemia, with nonspecific symptoms of hypercalcemia such as malaise, fatigue, depression, and diffuse aches and pains. hypercalcemia and hyperophosphatemia are evident on laboratory evaluation.