Hypomagnesemia and hypocalcemia after thyroidectomy: Prospective study

Hypomagnesemia after total thyroidectomy has not been studied extensively. Our anecdotal experience suggests that it may be important in some patients after thyroid excision. The hypomagnesemic hypocalcemic syndrome has been described in other disease states in which a state of Functional hypoparath yroidism exists. This study was designed to determine the incidence of hypo magnesemia after total thyroidectomy and relate it to hypocalcemia and symp toms during the postoperative period. A prospective study of all patients u ndergoing total thyroidectomy between September 1994 and July 1996 was perf ormed. Patient data, thyroid function, retrosternal extension, initial vers us reoperative surgery, operative details, parathyroid resection, and patho logy were recorded. Calcium, magnesium, electrolytes, blood count, liver fu nction tests, and albumin were measured prior to surgery and twice daily du ring the postoperative period. Fifty patients underwent total thyroidectomy : 68% were hypocalcemic, 72% were hypomagnesemic, and 36% were symptomatic during the postoperative period. Hypomagnesemia and gender were associated with hypocalcemia. Volume of fluid and neck dissection were associated with low magnesium levels. Hypomagnesemia and parathyroid resection were risk F actors for symptoms after thyroidectomy. No patients developed permanent hy poparathyroidism. Transient hypocalcemia and hypomagnesemia occur frequentl y after total thyroidectomy. The etiology of this phenomenon is probably mu ltifactorial. Patients are more likely to be symptomatic when both cations are low, and attempting to correct only hypocalcemia may prolong symptoms. It is important to monitor both calcium and magnesium levels after total th yroidectomy and to correct deficiencies to facilitate prompt resolution of symptoms.