Endocrine Abstracts

Introduction

Hypocalcaemia is a complication of total thyroidectomy (TT) and may be more frequent in patients with Graves’ disease. The reason for this increased risk is unclear and its occurrence has been associated with: ophthalmopathy severity, preoperative calcaemia and reimplantation of parathyroid glands.

Objectives

To evaluate the risk factors for transient hypocalcaemia (TH) and definitive hypoparathyroidism (DH) in patients undergoing total thyroidectomy for Graves’ disease.

Methods

Retrospective study of patients with Graves’ disease, who underwent TT between January/2016 and January/2020. Patients with histological diagnosis of malignant thyroid neoplasm or concomitant hyperparathyroidism were excluded. Clinical and laboratory data were collected from clinical files. In the statistical analysis, SPSS software (version 25.0) was used. The variables are expressed as mean and standard deviation, calculating the relative risk (RR) and considering a 95% confidence interval.

Results

49 patients (out of 71 operated) were selected according to the inclusion/exclusion criteria, 73.5% were men. Prevalence of TH was 49.0% and of DH 8.2%. There were no statistically significant differences between patients without (WPH) or with (PH) postoperative hypocalcaemia according to age, interval between diagnosis and surgery, gland weight, serum TSH, FT4, FT3, TRAB levels at diagnosis, or preoperative calcaemia. In the PH group, postoperative PTH levels were significantly lower (58.6 ± 5.9 vs. 23.9 ± 5.5 pg/ml; P < 0.01) and the length of hospital stay was significantly higher (4.3 ± 0.5 vs. 2.8 ± 0.1 days; P = 0.02). There was a statistically significant correlation between preoperative TRAB and postoperative PTH (r = –0.14; P < 0.05). For the 5 patients who underwent reimplantation of at least 1 parathyroid gland, all had hypocalcaemia: definitive hypoparathyroidism – 3; transient hypocalcaemia – 2. Thyroid orbitopathy was present in 30 patients (61%); these patients did not have a higher RR for occurrence of hypocalcaemia (RR = 0.77 [0.5–1.23]), transient hypocalcaemia (RR = 0.8 [0.47–1.39]) or definitive hypoparathyroidism (RR = 0.63 [0.1–4.12])

Conclusion

In this study, we found a high prevalence of postoperative hypocalcaemia and a correlation between postoperative PTH levels and TRAB levels at diagnosis. The reimplantation of at least 1 parathyroid gland predicts high risk for occurrence of hypocalcaemia, since in this sample all patients subjected to this intervention presented transient or definitive hypoparathyroidism. On the other hand, it was not found an association between orbitopathy and calcium-related postoperative complications.