P1428PERSISTENT HUNGRY BONE SYNDROME AND HYPOPARATHYROIDISM AFTER PARATHYROIDECTOMY FOR SECONDARY HYPERPARATHYROIDISM: ARE THERE RISK FACTORS?
Authors: Parshina Ekaterina , Zulkarnaev Aleksei , Novokshonov Konstantin , Kislyy Pavel , Tolkach Alexey , Chernikov Roman 
Published: June 2020

Abstract

Background and Aims
Hungry bone syndrome (HBS) and postoperative hypoparathyroidism both are important postoperative complications after parathyroidectomy (PTx) for severe secondary hyperparathyroidism (SHPT). There is still a lack of data in the literature concerning associated risk factors of the prolonged HBS and hypoparathyroidism after PTx. We aimed to explore the risk factors for HBS and postoperative persistent hypoparathyroidism development in a long-term period after surgery.

Method
We performed a retrospective analysis of 55 severe SHPT patients who underwent subtotal PTx or total PTx+AT in our clinic between 2011 and 2015 with follow-up period not less than 12 months. A general cohort was divided into subgroups according to their laboratory parameters in a year after PTx. Prolonged HBS was defined as a total serum calcium concentration less than 2,1 mmol/l after 1 year from surgery. Postoperative hypoparathyroidism was defined as a iPTH value less than 10 pg/mL after one year from surgery.

Results
In terms of prolonged HBS persistence a general cohort of 55 patients was divided into two subgroups: a HBS group of 27 patients (49,1%) with mean age of 45,6 ± 9,02 years and a non-HBS group of 49,6 patients (50,9%) with mean age of 45,6 ± 10,8 years. Mean dialysis vintage for HBS and non-HBS groups was 107,8 ± 52,4 and 97,4± 54,5 months, respectively. The PTH level dropped significantly in both groups on the 1st day after surgery when compared with preoperative values: from 134 [92,7-186] to 5,0 [2,1–17,7] pmol/l in non-HBS group (p&lt;0,001) and from 126 [101-223] to 4,1 [1,5-14,5] pmol/l in HBS group (p&lt;0,001). The immediate ionized calcium levels also decreased significantly in both groups: from 1,26 [1,2-1,3] to 0,89 [0,79-1,09] in non-HBS group (p&lt;0,001), and from 1,2 [1,11-1,29] to 0,88 [0,8-1,0] in HBS group (p&lt;0,001). In univariate analysis the postoperative iPTH showed no significant difference between the HBS and non-HBS groups (p= 0,614) as well as ionized Ca level (p= 0,5653), difference of PTH before/after surgery (ΔPTH) (p= 0,9133), age (p= 0,2575) and dialysis vintage (p= 0,6165). Neither gender (RR 0,75 [0,44; 1,277]; p = 0.4088), nor type of surgery (RR 0,81 [0,45; 1,456]; p = 0.5815) were associated with the long-term HBS persistence.
For 51 patients data of iPTH level in a 1 year after PTx were available; 21 patients (41,2 %) were included in the postoperative persistent hypoparathyroidism-positive group (hypoPT-positive), and 30 patients (58,8%) were included in the postoperative persistent hypoparathroidism-negative (hypoPT-negative) group. In both hypoPT-positive and hypoPT-negative groups postoperative iPTH levels were decreased after surgery with significant difference being compared between groups (1,0 [0,8-2,5] vs 12,6 [3,7-17,7] pmol/l, respectively; p= 0,0001). We observed a moderate positive correlation between iPTH levels on the 1st postoperative day and in a 1 year after PTx (ρ=0,548 [95% CI 0,314; 0,72]; p&lt;0,0001). Type of surgery was not associated with increased risk of prolonged hypoparathyroidism (RR=1.03 [0,569; 1,866]; p=0.922).

Conclusion
Prolonged persistence of HBS and postoperative hypoparathyroidism are common after PTx in patients with SHPT regardless the type of surgery. Neither laboratory (postoperative iPTH, ΔPTH, ionized Ca), nor demographic (gender, age, dialysis vintage) factors were not associated with HBS persistence in a long-term period after PTx. Only serum iPTH level on the 1st day after PTx is associated with prolonged hypoparathyroidism after surgery.