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Vitamin D status may impact parathyroid hormone levels after obesity surgery

Posted on: December 25, 2017   by  Missy Sturges & John Canell, MD


We are a society on the go. With a life filled with never ending checklists, most of which must be accomplished in front a computer, we are continuously driven into a sedentary lifestyle and convenient, fast-food fixes. This lifestyle evolution has proven to wreak havoc on our health. One of the primary indicators of this is the spike in obesity, vitamin D deficiency and an increased risk of chronic diseases.

Desperate to lose weight and improve overall health, many people have opted to undergo bariatric surgery. These surgical weight loss procedures essentially restrict the size of the stomach, and sometimes, remove a portion of the upper intestine to decrease nutrient intake and absorption. Though this procedure is mostly successful and has saved many lives, surgical weight loss has its risks. This may include surgical complications, nutrient deficiencies, secondary hyperparathyroidism (SHPT) and if left untreated, bone deterioration.

SHPT occurs in response to low blood calcium. When blood calcium is low, parathyroid hormone (PTH) is secreted to pull calcium from the bones to the blood, and signal the kidneys to produce more activated vitamin D. This will enable more calcium to be absorbed from the gut to provide to the bloodstream. However, during times of chronic vitamin D deficiency, less calcium is absorbed from the gut, leading the parathyroid hormone to remain elevated in an attempt to stimulate activation of vitamin D, thus drawing more calcium from the bones.

Despite the high prevalence of SHPT and the detrimental effects this can have on bone health, there remains a lack of consensus regarding the optimal dosage of vitamin D supplementation to manage this issue. Therefore, a new study aimed to determine how vitamin D levels may impact calcium and PTH levels in those who have undergone surgical weight loss surgery.

This study included 502 bariatric surgery patients between the ages of 22-64 years who underwent roux-en-Y gastric bypass surgery at the Oslo University Hospital in Norway. The researchers evaluated the patients vitamin D, calcium and PTH levels.

Here is what they found:

  • A total of 34% of patients experienced SHPT two years after their surgery.
  • Vitamin D status was associated with the prevalence of SHPT (p < 0.01).
  • 71% of individuals with vitamin D levels < 10 ng/ml (25 nmol/l) had SHPT.
  • 41% of those with levels < 20 ng/ml (50 nmol/l) had SHPT.
  • The risk for developing SHPT decreased as vitamin D levels increased.
  • 29% of those with SHTP had levels of > 20 ng/ml (RR: 0.64; CI: 0.50 – 0.81).
  • 27.7% of those with SHTP had levels > 30 ng/ml (75 nmol/l) (RR: 0.61; CI: 0.44 – 0.84).
  • 16% in those with SHTP had levels > 40 ng/ml (100 nmol/l) (RR: 0.35; CI: 0.14 – 0.84).
  • Vitamin D levels above 40 ng/ml (100 nmol/l) were associated with the lowest risk of developing SHPT compared to levels below 20 ng/ml (50 nmol/l) (RR: 0.35; CI: 0.14-0.88)
  • In addition, levels above 40 ng/ml were associated with the lowest PTH levels and most normal calcium levels.

The researchers concluded,

“Vitamin D deficient patients had the highest prevalence of SHPT two years after gastric bypass. PTH and the prevalence of SHPT were notably lower with 25(OH)D levels > 100 nmol/l, compared with lower target levels.”

The primary limitation of this study is its cross sectional design. Because this study was only able to show the relationship between vitamin D status and SHPT at one point in time, the researchers were unable to show how resolving vitamin D deficiency may impact PTH levels over time. In addition, the lack of diversity among the participants may have impaired the generalizability of these findings.

Nevertheless, this study provides further evidence to support vitamin D levels of at least 40 ng/ml are required for optimal health. The Vitamin D Council recommends adults supplement with 5,000-10,000 IU (125-250 mcg) vitamin D3 daily in order to reduce the risk of SHPT in those who have undergone a surgical weight loss procedure.

Have you undergone gastric bypass surgery and supplement with vitamin D? Please email us at [email protected] to share your experience with our team so that we can continue helping others with their health journey.


Sturges, M. & Cannell, JJ. Vitamin D status may impact parathyroid hormone levels after obesity surgery. The Vitamin D Council Blog & Newsletter, 12/2017.


Hewitt, S. et al. Relationships of serum 25-hydroxyvitamin D, ionized calcium and parathyroid hormone after obesity surgery. Clinical Endocrinology, 2017.

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