New study finds elevated parathyroid hormone may not be a risk factor for cardiovascular diseases

Posted on: September 10, 2014   by  Amber Tovey

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A recent study published in the American Heart Journal found that elevated parathyroid hormone levels are not a risk factor for cardiovascular diseases, contrary to previous research.

The parathyroid hormone’s (PTH) main job is to regulate calcium and phosphate levels. When calcium levels are low, PTH is secreted. PTH pulls calcium out of the bones and into the blood.

When someone has low levels of vitamin D, their body is not absorbing adequate amounts of calcium which results in an elevation of PTH levels.

Therefore, PTH has an inverse relationship with vitamin D. When vitamin D levels are low, PTH levels are usually high, meaning that elevated PTH levels, in most situations, can be considered a marker of vitamin D deficiency.

Previous research suggests that elevated PTH levels are associated with risk factors for cardiovascular diseases. On the other hand, higher vitamin D levels have been shown to improve cardiovascular health.

For example, elevated PTH levels have been linked to high blood pressure, while increased vitamin D levels have been shown to reduce blood pressure.

Inflammation is thought to contribute to cardiovascular disease and both PTH and vitamin D affect inflammation differently. Elevated PTH has pro-inflammatory effects and vitamin D has anti-inflammatory effects.

Because of this evidence, researchers hypothesized that elevated PTH levels would be associated with the incidence of cardiovascular diseases.

To test their hypothesis, they conducted a study to examine the relationship between PTH levels and incidence of cardiovascular events.

The researchers looked at data from 10,392 adults from the Atherosclerosis Risk in Communities (ARIC) study. ARIC is a large cohort study which was created to investigate the causes and outcomes of atherosclerosis.

The researchers measured the PTH levels from stored blood samples and compared this to the participants’ incidence of cardiovascular outcomes, including coronary heart disease, stroke, mortality, and heart failure, over an average follow up of 19 years.

Here’s what the researchers found:

  • PTH levels were not significantly associated with any of the cardiovascular outcomes.
  • Participants with elevated PTH levels were not at an increased risk for cardiovascular diseases.
  • Interestingly, participants in the group with the highest PTH levels had a 27% decreased risk for cardiovascular mortality.

The researchers stated,

“This large, population-based, prospective ARIC study of whites and African Americans did not find any independent positive associations of PTH with incident CVD outcomes, including CHD, stroke, heart failure, peripheral artery disease, atrial fibrillation, or CVD mortality.”

The researchers note that the analyses were based on a single PTH test, which only moderately correlated with PTH levels taken three years later. The participants’ PTH levels may have changed over time, and therefore, may have skewed the results.

The study’s null results may add to the evidence for vitamin D’s role in heart health. As elevated PTH can be seen as a marker for vitamin D deficiency, the lack of association seen in this study between PTH and cardiovascular outcomes may mean that vitamin D influences heart health to a greater degree than PTH.

Since vitamin D levels weren’t measured in this study, further research is needed in which both vitamin D and PTH are examined to determine the full extent of their relationship to cardiovascular health.

Source

Folsom R, et al. Parathyroid hormone concentration and risk of cardiovascular diseases: The Atherosclerosis Risk in Communities (ARIC) study. American Heart Journal, 2014.

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