Yoshida and coworkers* noted that a patient with myotonic dystrophy (a neuromuscular disease) had elevated blood calcium levels. A search of the clinical literature revealed other case reports that suggested a problem with the parathyroid glands in patients with myotonic dystrophy. They hypothesized that patients with myotonic dystrophy also have hyperparathyroidism, a syndrome caused by an overactive parathyroid gland. To test this hypothesis, they measured the body’s response to a calcium challenge in patients with myotonic dystrophy, patients with other types of dystrophy (nonmyotonic dystrophy), and normal subjects. One of the biochemical variables they measured was the amount of cyclic AMP (cAMP) excreted by the kidneys (the data are in Table D-18, Appendix D). Elevated renal cAMP excretion would be consistent with hyperparathyroidism. Is there any evidence that cAMP excretion is elevated in myotonic dystrophic subjects?