Hypocalcemia as a post-thyroidectomy complication in patients with Graves' disease

Abstract

Abstract: 

Graves' disease (GD) can be surgically treated and present complications like postoperative hypocalcemia.

Objectives: (1) Evaluate the incidence of postoperative hypocalcemia in patients with GD. (2) Find out if hypocalcemia incidence is grater in thyroidectomized patients due to other causes. (3) Determine whether hypovitaminosis D is predictive of hypocalcemia. (4) Establish the usefulness of vitamin D (VD) substitution.

We conducted an analytic longitudinal observational cohort study. We included 12 patients with GD (Graves group) and 23 thyroidectomized patients as a result of other benign thyroid diseases (BTD), both sexes, 18 to 70 years old. There was a total of 3 males (9%) and 32 females (91%). Preoperative calcemia was (: 9.1 ± 0.5 mg/dL). Postoperative calcemia was (: 8.6 ± 0.6 mg/dL) after 8 hours, (: 8.6 ± 0.6 mg/dL) after 12 hours, (: 8.9 ± 0.6 mg/dL) after 1 month and (: 9 ± 0.8 mg/dL) 6 months after surgery. Preoperative VD was (: 23.1 ± 10 ng/mL).

Hypocalcemia was defined as calcemia < 8.5 mg/dL. Transient calcemia was defined as less than 6 months. Permanent calcemia was defined as over 6 months.

Within GD group, hypocalcemia incidence was 54.4% (6 patients) 8 hours after surgery, 45.5% (4 patients) 12 hours after surgery, 16.7% (2 patients) 1 month after surgery and 33% (4 patients) 6 months after surgery. Within BTD group, hypocalcemia incidence was 26.1% (6 patients) 8 hours after surgery, 26.1% (6 patients) 12 hours after surgery, 13% (3 patients) 1 month after surgery and 22% (5 patients) 6 months after surgery (p>0.05). Preoperative VD in Graves group vs. BTD group (15.3 ± 4.5 ng/dl vs. 25.3 ± 10 ng/dl) (p<0.05). With preoperative VD replacement, we observed that 70% of the patients (n:7) didn't present postoperative hypocalcemia, while 30% (n:3) did. Without preoperative replacement, we observed that 40% of them (n:10) didn't present hypocalcemia, while 60% (n:15) did. (p>0.05).

We noticed that patients with GD have a higher incidence of transient and permanent hypocalcemia than patients in the BTD group. Also, none within the GD group had enough preoperative VD; therefore, hypovitaminosis D might be a predictive factor for hypocalcemia. Although a larger sample is needed, considering sufficient preoperative VD levels would be advisable to avoid postoperative hypocalcemias.