Study: Vitamin D Metabolism Altered in Cushing’s Patients

Marisa Wexler MS avatar

by Marisa Wexler MS |

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In people with Cushing’s disease, the activity of an enzyme that breaks down vitamin D is altered, which may affect the effectiveness of vitamin D dietary supplements, according to a new study.

The study, “Assessment of Vitamin D Metabolism in Patients with Cushing’s Disease in Response to 150,000 IU Cholecalciferol Treatment,” was published in the journal Nutrients.

Cushing’s disease is caused by a tumor in the brain’s pituitary gland, resulting in abnormally high levels of the stress hormone cortisol. Cortisol helps regulate many important bodily functions, one of which is vitamin D metabolism. This vitamin plays a critical role in maintaining bone health.

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However, it is not well-understood how the excess cortisol levels that characterize Cushing’s disease affect vitamin D metabolism in the body. Here, a team of scientists in Russia conducted a series of experiments to gain more insight.

Their study included 30 people with Cushing’s disease, and an equal number of participants with no apparent health problems who served as controls.

Most participants in both groups were female, with an average age in the mid-30s. There were no differences between the groups in terms of reported smoking status, physical activity, diet, or sunlight exposure, which directly affects the production of vitamin D in the body.

Researchers collected blood samples from all participants to measure the levels of vitamin D and a number of related molecules. For all participants except two of the controls, levels also were measured on three different time-points after participants took a high dose (150,000 international units) of cholecalciferol, or vitamin D3, which is a form of vitamin D often found in food.

A notable finding of this analysis was that the ratio of two vitamin D metabolites — 25(OH)D3 and 24,25(OH)2D3 — was higher in Cushing’s disease patients, both initially and after taking cholecalciferol.

According to researchers, this suggests that the activity of an enzyme called 24-hydroxylase, which is the main enzyme responsible for breaking down, or catabolizing, vitamin D in the body, is “consistently reduced” in people with Cushing’s disease.

“This altered activity of the principal vitamin D catabolism might influence the effectiveness of cholecalciferol treatment,” the researchers wrote.

Researchers also noted several other abnormalities in vitamin D metabolism in Cushing’s disease patients. These included, for instance, the levels of another vitamin D metabolite called 25(OH)D that were lower initially, but then comparable to those seen in controls following the administration of cholecalciferol.

Scientists called for further research to better understand how vitamin D metabolism is affected in Cushing’s disease, and what consequences this may have for clinical care.