Which of the following lab results would indicate a slowdown in the rate of parathyroid hormone secretion?

a. Increased serum calcium levels
b. Decreased serum calcium levels
c. Decreased levels of TSH
d. Increased levels of TSH

ANS: A
An increase, not a decrease, in serum calcium inhibits parathyroid hormone (PTH) secretion. Thyroid-stimulating hormone would not affect PTH secretion.