From the Guidelines
Yes, it is possible for someone to have normal calcium levels, elevated Parathyroid Hormone (PTH), and decreased Alkaline Phosphatase (ALP). This combination of laboratory findings can be seen in normocalcemic primary hyperparathyroidism, a variant of primary hyperparathyroidism characterized by elevated PTH concentrations with normal calcium values, as discussed in a 2019 review published in Endocrine Reviews 1. The presence of elevated PTH with normal calcium levels suggests that the parathyroid glands are overactive, but the body is still able to maintain normal calcium levels. The decreased ALP is an unusual finding, as ALP is typically normal or elevated in hyperparathyroidism due to increased bone turnover.
Some possible explanations for decreased ALP include:
- Hypophosphatasia, a rare genetic disorder
- Malnutrition
- Vitamin C deficiency
- Certain medications that suppress bone formation Further investigation is necessary to determine the underlying cause of this combination of laboratory findings, including measurement of:
- Vitamin D levels
- Phosphate
- Magnesium
- Liver function tests
- Kidney function tests Treatment would be directed at the specific underlying condition rather than the laboratory abnormalities themselves. Accurate measurement of PTH is crucial in identifying patients with normocalcemic primary hyperparathyroidism, as emphasized in the 2019 review 1.
From the Research
Calcium, PTH, and ALP Levels
- Normal circulating levels of calcium, elevated Parathyroid Hormone (PTH), and decreased Alkaline Phosphatase (ALP) can occur in certain conditions.
- According to 2, primary hyperparathyroidism (PHP) may feature hypercalcemia and elevated or inappropriate PTH elevation, but it can also be normocalcemic.
- In cases of PHP, calcium loading may be necessary to diagnose the condition, and it can be accompanied by renal complications and/or osteoporosis.
Relationship Between PTH and Calcium
- PTH is a hypercalcemic hormone that acts on kidneys, bone, and intestine to promote calcium release from the bone, renal calcium reabsorption, and phosphate excretion 2.
- The relationship between PTH and calcium is tightly regulated, with PTH secretion reduced when extracellular fluid (ECF) calcium is in the hypercalcemic range, and renal 1,25(OH)2D production decreased 3.
ALP and Bone Health
- ALP is an enzyme involved in bone formation, and decreased levels can indicate impaired bone health.
- However, the studies provided do not directly address the relationship between decreased ALP and elevated PTH with normal calcium levels.
- It is essential to consider the underlying cause of the elevated PTH and decreased ALP to determine the appropriate course of action.
Clinical Implications
- The combination of normal calcium levels, elevated PTH, and decreased ALP may require further investigation to determine the underlying cause.
- According to 4, the initial approach to evaluating hypercalcemia involves measuring serum intact PTH to distinguish between PTH-dependent and PTH-independent causes.
- Treatment depends on the etiology of the condition, and a definitive diagnosis is necessary to determine the appropriate course of action 5.