Thyroidectomy had been performed in 296 patients (235 females and 61 males). TT had been performed in 36 of them and TT plus LN dissection in the other 260. Patients` characteristics were indicated in . The patients’ median age at the time of surgery was 54 years (range: 14-86). All patients were followed up. The median follow-up period was seven months (range: 7-20). On POD 1, 73 patients were hypocalcemic.
The serum iPTH value on POD 1 was within the normal range in 67 of the 296 patients (). The serum iPTH level and calcium level were within the normal range in 63 patients, and six of them received vitamin D and/or calcium supplementation in order to prevent hypocalcemia under doctor’s judgment. One parathyroid gland had been preserved in situ in 13 of the 63 eucalcemic patients with normal parathyroid function, two had been preserved in situ in 35 of them, three in seven of them, and four in eight of them. Postoperative hypocalcemia developed in four of the 67 patients with a normal iPTH value on POD 1. Two of the four patients with postoperative hypocalcemia did not receive any supplementation because their hypocalcemia was mild and they were asymptomatic. The serum iPTH was below the normal range in 229 patients on POD 1. Postoperative hypocalcemia developed in 69 of these 229 patients on POD 1, and calcium supplementation and vitamin D supplementation were started. The serum calcium value on POD 1 was within the normal range in 160 of the 229 patients with postoperative hypoparathyroidism. One of these 160 patients did not require oral calcium supplementation to maintain normocalcemia, but 157 of them received calcium and vitamin D supplementation. Serum iPTH value sensitivity on POD 1 to predict hypocalcemia was 94.5%, and serum iPTH value specificity on POD 1 to predict hypocalcemia was 28.3%.
Flow Chart of the Patient Population Investigated on Postoperative Day 1. iPTH, Intact Parathyroid Hormone; Vit D, Vitamin D
None of the parathyroid glands were preserved in situ in 41 patients, all of them developed hypoparathyroidism on POD 1. One parathyroid gland was preserved in situ in 106 patients, 91 of them developed hypoparathyroidism on POD 1 (86%). Two parathyroid glands were preserved in situ in 128 patients, 91 of them developed hypoparathyroidism on POD 1 (71%). Three parathyroid glands were preserved in situ in 11 patients, four of them developed hypoparathyroidism on POD 1 (36%). And four parathyroid glands were preserved in situ in ten patients, two of them developed hypoparathyroidism on POD 1 (20%). The incidence of hypoparathyroidism on POD 1 was significantly higher in the group with smaller number of preserved parathyroid glands in situ (P < 0.01).
During the follow-up period the serum iPTH level of 192 out of a total 229 patients who developed hypoparathyroidism on POD 1 recovered to the normal range. The median duration of the hypoparathyroidism was three months. In 52 of them parathyroid function recovered within one month after surgery. Their average serum iPTH value on POD 1 was 7.6 pg/mL. The average iPTH value on POD 1 of the 192 patients with transient hypoparathyroidism was 6.7 pg/mL. Thirty-seven patients developed permanent hypoparathyroidism, and their average serum iPTH value on POD1 was 4.9 pg/mL. There was a significant difference between the serum iPTH values on POD 1 of the transient and the permanent hypoparathyroidism groups (P < 0.01).
The incidence of hypoparathyroidism on POD 1 was higher in the TT plus LN dissection group than in the TT group (). The average serum iPTH value on POD 1 was 15.1 pg/mL in the group who had undergone TT alone versus 8.8 pg/mL in the group undergone TT plus LN dissection (P < 0.01). Permanent hypoparathyroidism developed in six TT patients and in 31 TT plus LN dissection patients. The incidence of permanent hypoparathyroidism was significantly higher in the TT plus LN dissection group than in the TT group. None of the parathyroid grafts that had been successfully implanted in the patients with permanent hypoparathyroidism ceased to function later. The incidence of permanent hypoparathyroidism was significantly higher in the smaller numbers of present (preserved + autotransplanted) parathyroid glands (P < 0.01). Two patients ,whose all four parathyroid glands had been preserved in situ developed permanent postoperative hypoparathyroidism (their serum iPTH values on POD 1 were 5.3 pg/mL and 11.3 pg/mL, respectively), but their serum iPTH levels gradually increased to 13.1 pg/mL and 12.5 pg/mL, respectively, by 11 months after TT, and vitamin D supplementation had been continued in both patients.
Incidence of Hypoparathyroidism on Postoperative Day 1
There was no correlation between the time required for the low iPTH values on POD 1 to recover to within the normal range and the number of present parathyroid glands in the patients with transient hypoparathyroidism. The average periods of serum iPTH level rising to the normal range after the surgery were five months in the autotransplanted parathyroid gland group and three months in the two autotransplanted parathyroid gland groups, the three autotransplanted parathyroid gland group, and the four autotransplanted parathyroid gland group (P = 0.58).