Professional and Linguistic Assessments Board (PLAB) Practice Exam

What condition is associated with high PTH levels and normal or low calcium levels?

1. Tertiary hyperparathyroidism

2. Primary hyperparathyroidism

3. Secondary hyperparathyroidism

4. Hypoparathyroidism

The correct answer is: Secondary hyperparathyroidism

High parathyroid hormone (PTH) levels along with normal or low calcium levels are indicative of secondary hyperparathyroidism. This condition often occurs in response to chronic kidney disease (CKD), where the kidneys fail to adequately excrete phosphate, leading to elevated phosphate levels and subsequently lower calcium levels due to the binding of calcium by phosphate. In response to low calcium levels, the parathyroid glands increase PTH production in an attempt to normalize calcium levels by promoting calcium release from bones, increasing intestinal calcium absorption, and enhancing renal tubular reabsorption of calcium. However, because the underlying issue is the renal failure affecting calcium absorption and phosphate retention, calcium levels may remain low or normal despite high PTH levels. In contrast, primary hyperparathyroidism typically presents with elevated calcium levels alongside elevated PTH levels due to an overactive parathyroid gland. Tertiary hyperparathyroidism, which can occur following long-term secondary hyperparathyroidism, usually involves high PTH and high calcium levels as the parathyroid glands become autonomous. Hypoparathyroidism is characterized by low PTH levels and usually results in low calcium levels. Thus, the specific combination of high PTH with normal or low calcium is most accurately associated with