hyperparathyroidism
Hyperparathyroidism is the condition of too much parathyroid hormone. Imagine the calcium thermostat stuck on high: the parathyroids keep shouting raise calcium even when there is already plenty, so the body steadily pulls calcium out of bone and into the blood.
The most common form, primary hyperparathyroidism, comes from one parathyroid gland growing a benign tumor (adenoma) that ignores feedback and pumps out PTH on its own, raising blood calcium. A different form, secondary hyperparathyroidism, is an appropriate response gone chronic: in kidney disease or vitamin D deficiency the glands enlarge and overwork trying to fix a low calcium signal. Over years, secondary disease can become autonomous (tertiary).
The relentless PTH drives bone resorption, thinning the skeleton and sometimes causing classic bone changes, while raising urine calcium enough to form kidney stones. Many people today are caught early with only mildly high calcium and few symptoms. Definitive treatment of primary disease is surgery to remove the overactive gland, which can normalize calcium and protect the bones.
A woman with osteoporosis worse than expected for her age is tested and found to have an adenoma in one parathyroid gland; removing it halts the bone loss.
Unexplained bone loss can unmask a hidden parathyroid adenoma.
Primary hyperparathyroidism shows high calcium with high PTH; secondary shows low or normal calcium with high PTH. Reading the two values together tells the forms apart.