Prediction and management of hypo parathyrodism after Thyroidectomy for toxic goiter

Abstract

Toxic goiter is a syndrome characterized by symptoms and signs of hyper metabolism and increased sympathetic nervous system activity that result from excessive thyroid hormone production. The most common cause of thyrotoxicosis is Gravis' disease which account for 60% to 90% of all cases of thyrotoxicosis. Hyperthyroidism is easily confirmed by the presence of elevated serum levels of thyroxin (T4) or triiodothyronine (T3) and suppressed serum levels of thyroid stimulating hormone or antimicrosomal antithyroglobulin and antiperioxidase antibodies are often encountered. The 24 hours radioiodine (RAI) uptake is often elevated. Treatment options for thyrotoxicosis include anti thyroid medications, radioactive iodine therapy, and thyroidectomy. Although most hyperthyroid patients (especially those with Graves' disease) are treated medically, thyroidectomy has several distinct advantages including; rapid resolution, relative safety, high success rate, simultaneous tissue diagnosis, cosmetic improvement with goiter removal, ability to salvage medical failures, acceptable alternative for non-compliant patients and less risk of exacerbating ophthalmopathy. The extent of thyroidectomy depends on several factors. A total thyroidectomy is indicated in patients with a coexisting malignancy of the thyroid or parathyroid cancer, multiple endocrine neoplasia, severe thyrotoxicosis. Hypoparathyrodism after surgery may be temporary or permanent. It is most frequent with total thyroidectomy. Symptoms include peri-oral tingling and numbness, followed by similar sensations in the digits and a positive chvostek's sign, and may progress to carpopedal spasm. Hypocalcemia increases anxiety frequently, respiratory alkalosis, hyperventilation, and tetany may occur . The incidence of permenant hypoparathyrodism after thyroid surgery is less than 2%. Transient postoperative hypocalemia occurs in up 50% of cases after thyroidectomy. Although serial calcium levels correlate with development of symptomatic hypocalcemia, they may not be judged until 36 to 72 hours postoperatively. Immediately post-operative parathyroid assay result, available within 15 to 20 minutes postoperatively, may predict parathyroid dysfunction after thyroid surgery. It has the potential to reduce mortality and morbidity from hypocalcemia, to reduce remission rate, and to allow early discharge by avoiding the need for serial calcium levels in patients found to be at low risk. When used intra-operatively, it assists in identification of patients requiring auto transplantation for questionably viable glands. This study was conducted at the department of surgery at El Demerdash Hospital and Shebin El kom Teaching Hospital on thirty patients with toxic goiter. All patients were prepared for surgery by anti thyroid drugs (carbimazole) and β-blocking drugs. Iodine was given with anti thyroid drugs or β-blocking drugs for 10 days before surgery, to reduce vascularity of the gland. Inclusion criteria: * Patient with toxic goiter based on symptoms and signs. * Age group between 20 and 50 years old patients. * Patients with no other problems which can affect serum calcium. Exclusion criteria : * solitary thyroid nodule. * Disturbed parathyroid hormone level. * Disturbed calcium level in the blood. All patients were screened for parathyroid hormone level and serum calcium level pre-operative, immediately post-operative, one and four weeks post-operative. In case of presence low PTH which predict presence of hypocalcaemia treatment was started by calcium substitution. All patients were asked about presence of symptoms and signs of hypocalemia in the form of peri-oral tingling and numbness, followed by similar sensations in the digits and a positive chvostek's sign, and that progress to carpopedal spasm. The results of total and subtotal thyroidectomy were compared for presence of post-operative hypo parathyroidism. The study concluded that PTH assay checked immediate post operative,1 week & 4 week after thyroidectomy provides excellent accuracy in determining which patients who will become significantly hypocalcemic. This predictive power was improved to nearly perfect when early calcium levels were considered as well. Obtaining preoperative PTH and calcium values is suggested so that percentage decreases can be calculated. Routine use of these assays should be considered to improve the postoperative management of patients with total and completion thyroidectomy. Patients identified as low risk for hypocalcemia could be discharged sooner. Conversely, patients identified as high risk for hypocalcemia could be treated earlier, potentially shortening the duration of their hypocalcemic symptoms and hospitalization.