What is a key characteristic of tertiary hyperparathyroidism?

A key characteristic of tertiary hyperparathyroidism is that parathyroid hormone (PTH) levels are inappropriately high. This condition typically arises after prolonged stimulation of the parathyroid glands, often seen in patients with chronic kidney disease. In this scenario, the parathyroid glands become hyperplastic and continue to secrete PTH even when calcium levels may be normal or high due to a compensatory mechanism in response to prolonged low calcium levels caused by renal failure.

In this context, continuous high PTH secretion by the hyperplastic parathyroid glands occurs despite the body’s regulatory feedback mechanisms indicating that calcium levels should be adjusted. As a result, the inappropriate elevation of PTH leads to persistent hyperparathyroidism, which is a hallmark of this condition.

The other options do not accurately represent the characteristics of tertiary hyperparathyroidism. For instance, the glands do not respond effectively to regulatory feedback in tertiary hyperparathyroidism, making the first option incorrect. Calcium levels can be variable but are often elevated or at least not low when tertiary hyperparathyroidism is present, thus making the second option inaccurate as well. Phosphate levels in tertiary hyperparathyroidism typically do not remain consistently low, especially in cases where chronic kidney disease