HYPOCALCEMIA FOLLOWING THYROIDECTOMY; A PROSPECTIVE STUDY IN BASRA, IRAQ

This study aimed to find out the frequency of hypocalcemia in different thyroid procedures and the risk factors for its development. One hundred thirty six patients underwent different thyroid surgeries for different thyroid diseases in the Surgical and Otolaryngology Departments of Basrah Teaching Hospital for three years from July 2016 to July 2019. Patients mean age was 34.8±7.5 years (range: 18-65 years). Male to Female ratio was 2:5. Of the total 136 patients, 35 patients underwent isthmusectomy and lobectomy, no case of hypocalcemia was reported (0%). Out of 71 patients who underwent sub-total thyroidectomy, three of them developed hypocalcemia (4.2 %). Out of 30 patients who underwent near-total or total thyroidectomy, nine of them developed hypocalcemia (30%). Whether the inferior thyroid artery was ligated or not, there was no significant difference in the development of hypocalcemia. Of the total 136 patients, 129 patients had benign pathology, 9 of them developed hypocalcemia (6.9 %); 7 patients had malignant pathology; 3 of them developed hypocalcemia (42.8%). In conclusion, the frequency of hypocalcemia is correlated with the extent of thyroid resection; and it is more in malignant lesions but in most of the patients it was transient.


Introduction
he term thyroid gland (Greek thyroidies) means shield-shaped 1 . Surgery is the treatment of choice for majority of thyroid pathology 1,2 . Thyroid surgery was hazardous until the mid-19th century when advances in general anesthesia, antisepsis, and hemostasis enabled surgeons to perform thyroid surgery with significantly reduced mortality. Nowadays surgical procedures in thyroid gland are generally safe and well tolerated. However, the occasional complications following such surgery may be life threatening or at least permanently disabling 3 . Hypocalcemia may occur secondary to surgical trauma, devascularization, intentional removal of parathyroid gland, total thyroidectomy and the degree of invasion by tumor 1 . Post-thyroidectomy hypocalcemia is an early complication; therefore careful observation of the patients should be done especially for those categorized as high risk patients in the postoperative period. Several studies showed that transient hypocalcemia prevalence rate range is 6.8-46%, while permanent hypocalcemia rate vary from (0-3%) [4][5][6][7][8][9] . The recommended surgical strategy is; meticulous dissection and preservation of the parathyroid glands with their blood supply, while removal of one gland is not T Bas J Surg, June, 26, 2020 associated with postoperative hypocalcemia; the same cannot be seen when two or more glands are removed.

Patients and methods
This prospective study was done at the General Surgery and Otolaryngology units in Basrah Teaching Hospital from January 2017 to January 2020. One hundred and thirty six patients (40 males and 96 females) with variety of thyroid diseases were admitted for different thyroid surgeries. Patients were interviewed prior to surgery about their sociodemographic characteristics.
Complete history, examination and investigations (including serum calcium level) were done preoperatively. At the operation, the risk factors for post-operative hypocalcemia were documented such as: Truncal ligation of inferior thyroid artery, the extent of thyroidectomy (isthmusectomy, lobectomy, subtotal thyroidectomy and near total thyroidectomy). All specimens were sent for histopathological examination. Measurement of serum calcium level was done for all patients at first post-operative day and the day of hospital discharge usually (3)(4)(5) days. Written informed consent was obtained from each patient before enrollment in the study following a detailed explanation of the objectives and protocol of the study. This study was approved by the Ethical Committee in Basrah Teaching Hospital. The data were analyzed using the SPSS (SPSS Inc., Chicago, IL, USA) version 23. Chi-square test was used to find the significance of differences in categorical parameters.

Results
One     There was significant relation between postoperative hypocalcemia and the type of thyroid surgery (P-value=0.001). In isthmusectomy and lobectomy cases, no postoperative hypocalcemia was reported. In 71 patients who underwent subtotal thyroidectomy, 3 patients (4.23%) developed hypocalcemia while, in 30 patients who underwent near total thyroidectomy, 9 patients (30%) developed postoperative hypocalcemia as shown in table III.

Discussion
Hypocalcemia is defined as a serum calcium level under 8 mg/dl for at least two consecutive measurements, and hypocalcaemia is considered to be severe when the patient experienced clinical symptoms and signs of hypocalcemia. Permanent hypoparathyroidism is defined by the requirement for vitamin D or calcium supplementation to maintain eucalcemia for one year after thyroidectomy. One hundred thirty six patients were enrolled in this prospective study, forty patients were males and ninety-six patients were females, with a male to female ratio 2:5. In other studies 1,10,11 , the male to female ratio may be as low as 1:8. The most common age group for patients with goiter at time of presentation was 20-40 year of age 11 . In this study, most of the patients were in the age group (30-39) year of age (39.7 %), with little number of patient below 20 years and over 50 years. The most common type of goiter at presentation is multinodular goiter followed by clinically solitary nodule 11 . In our study, similar result was obtained as 61% of the patients presented with multinodular goiter and 33.8% with solitary nodule. Most of the patients with goiter were presented with euthyroid state 11 . In our study, 75% were euthyroid, 23.5% were hyperthyroid, and 1.4% were hypothyroid. The standard surgical procedure for multinodular goiter is subtotal thyroidectomy, and for carcinoma of thyroid diagnosed preoperatively is near total or total thyroidectomy 1,12 . In this study, subtotal thyroidectomy was done in 52.2% of the patients while near-total thyroidectomy was done in 22%. In spite of the fact that carcinoma was diagnosed in 7 patients only, the commonest histopathological finding in thyroidectomy specimens was nodular colloid goiter (68.8%) 11 . The incidence of cancer in goiter is 6.4% in one study in our country 11 . In our study, nodular colloid goiter was found in 83.8% of specimens and the incidence of cancer was 5.14%, which was similar to Barnouti et al 11 . The incidence of transient postoperative hypocalcemia and permanent hypoparathyroidism is variable from 6.8-46% for transient hypocalcemia, 0-33% for permanent hypocalcemia [4][5][6][7][8][9] . In this study, the incidence of transient hypocalcemia and permanent hypoparathyroidism was 6.6% and 2.2% respectively. Analysis of risk factors for development of postoperative hypocalcemia showed that; no significant statistical difference between truncal ligation of inferior thyroid artery versus ligation of the branches of inferior thyroid artery at the capsule of thyroid gland 10 On the other hand, the incidence of hypocalcemia was higher in near-total or total thyroidectomy (9 out of 30 patients) (30%), while in subtotal thyroidectomy; the incidence was (3 out of 71 patients) (4.2%). This result is similar to that obtained in other studies like Van Gregory et al 1 and Hany Ali et al 14 . In our study, the incidence of hypocalcemia was more in malignant tumors than a benign disease (3 out of 7 patients) versus (9 out of 129 patients) (42.8%) versus (6.9%). This result was similar to that in other studies like Van Gregory et al 1 , Hany Ali et al 14 and Lamade et al 15 .
In conclusion, morbidity in thyroid surgery like postoperative hypocalcemia is related to the state of the parathyroid gland during surgery in many cases. In most of post-thyroidectomy cases, hypocalcemia was transient and occured in early postoperative period. The extent of thyroid resection is a risk factor for the onset of hypocalcemia, also malignant thyroid disease is a risk factor for hypocalcemia.