Hyperparathyroidism can occur when an adenoma (benign tumor) forms on one of the parathyroid glands. Which of the following are most likely to occur in a patient with a parathyroid adenoma? 
A. Increased fragility of bones

B. Increased risk of renal calculi

C. Spasms of skeletal muscles

D. Decreased calcium levels

In hyperparathyroidism, there is increased bone resorption by osteoclasts leading to osteoporosis which makes the bones fragile. Blood calcium levels are elevated due to bone resorption. High blood calcium level promotes the formation of renal calculi (kidney stones). Muscle spasms and tetany (sustained contraction) of skeletal muscle are due to hypoparathyroidism.