Benefits of Parathyroidectomy Run Far Deeper Than PTH Normalization

SEATTLE -- Parathyroidectomy helped reverse disrupted levels of inflammatory cytokines and vitamin D metabolites in patients with primary hyperparathyroidism (PHPT), a researcher suggested here.

After 50 patients, newly diagnosed with PHPT, underwent parathyroidectomy, serum intact parathyroid hormone (PTH) levels returned to the normal range within 3 months (115.6±38.9 to 42.6±24.5 pg/mL, P<0.001), said Xiangbing Wang MD, PhD, of Rutgers University Robert Wood Johnson Medical School in New Brunswick, New Jersey.

Also as expected after this surgery, calcium levels returned to the normal range (11.0±0.5 to 9.7±0.4 mg/dL, P<0.001).

But these weren't the only levels to significantly change after surgery, he explained at the American Association of Clinical Endocrinology (AACE) annual meeting.

There was also a significant increase seen in serum total 25OHD (28.2±8.8 to 39.1±13.7 ng/mL) and measured free 25OHD (4.9±2.0 to 7.6±2.3 pg/mL) after parathyroidectomy surgery. Vitamin D binding protein (DBP) levels also normalized, increasing from 35.9±7.4 mg/dL to 43.4±8.6 mg/dL.

Wang emphasized that both serum 25OHD and DBP levels started out significantly lower in PHPT patients when compared with age and BMI-matched controls. But a key finding according to Wang was that there were no baseline differences between the two groups when it came to measured free 25OHD levels.

"Maybe low DBP is one of the mechanisms of the low total vitamin D in this kind of patient," suggested Wang.

"A lot of us are not routinely checking vitamin DBP in my practice," added AACE session moderator Thanh Hoang, DO, of Walter Reed National Military Medical Center in Silver Spring, Maryland. "We usually go with total 25OHD. And if its low, I usually replete them before the surgery. But this is very good information."

On top of that, there was also a significant decrease noted in two inflammatory cytokines -- interleukin (IL)-6 (15.6±9.2 to 2.9±1.6 pg/mL) and MCP-1 (407.6±141.8 to 320.3±149.5) -- both of which returned back to the normal range. Both IL-6 and MCP-1 were positively correlated with PTH, Wang explained, while DBP was inversely correlated with PTH and IL-6.

"Our suggestion is that PTH level may suppress the liver production of the DBP," said Wang. "Also, the IL-6 -- the inflammation cytokine -- may also inhibit the DBP production by the liver."

"Chronic increased PTH level is associated with obesity and coronary artery disease with PHPT patients," he added. "This may be related to the increased cytokine -- IL-6 and MCP-1. After surgery, these levels come back to normal."

"Parathyroidectomy reduced cytokine and increased the total and free vitamin D and increased the DBP. This benefit may be related to decreased risk for coronary artery disease risk in these patients," said Wang.

"Compared to medical treatment, the parathyroidectomy may have some additional benefits [beyond] decreased calcium and decreased PTH," he said. "There may [also] be a decreased risk for cardiovascular risk factors with decreased inflammation cytokines."

Two levels that didn't significantly change after surgery were IL-10 (5.3±8.0 to 5.3±6.6) and C-reactive protein (4.3±4.5 to 5.5±6.3 mg/L). "IL-6 is the inflammation factor [that] contributes to cardiovascular [disease]. IL-10 actually has some benefit for cardiovascular disease," he pointed out.

One member of the audience asked what Wang would advise for PHPT who may not check off all the clinical guideline criteria for parathyroidectomy yet, but either have cardiovascular disease or are at high risk.

"According to our data...[and because] it's a minimally invasive surgery, if the patient has a high PTH -- even if they don't reach the guideline [criteria] -- I think parathyroidectomy have some additional benefits than just monitoring them," he suggested.

Data on 50 patients treated at Rutgers Robert Wood Johnson University Hospital were pulled for the study. A total of 28 of these patients returned for their 3-month post-surgery follow-up visit. Patients were newly diagnosed with PHPT and were between the ages of 20 to 80; had an elevated serum calcium above 10.4 mg/dL; elevated PTH above 65 pg/mL; and 24-h urine calcium above 100 mg, plus normal liver and kidney function.

The majority of patients were female (74%) with an average age of 60.

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