Post‐operative partial hypoparathyroidism: an under‐recognized disorder

BACKGROUND: Permanent hypoparathyroidism is a well-recognized complication of total thyroidectomy, and a commonly reported clinical indicator of that procedure. However, a small number of patients still require ongoing calcium supplementation post-operatively in order to avoid the symptoms of hypocalcaemia, despite a normal serum parathyroid hormone level. The aim of this study was to characterize this disorder of post-operative partial hypoparathyroidism and to identify any risk factors. METHODS: A retrospective study of patients undergoing a total thyroidectomy was performed. Patients with permanent hypoparathyroidism were excluded. Patients completed a telephone interview and had serum calcium and parathyroid hormone (PTH) measured. Patient demographics, operative indications and intervention, the number of parathyroid glands autotransplanted, the presence of ongoing symptoms and calcium requirements were documented. RESULTS: One hundred ninety-six patients participated. The overall rate of permanent hypoparathyroidism over the duration of the study was 0.77%. An additional 10 (5%) patients were identified with a normal PTH level but who were still requiring calcium supplementation to prevent the symptoms associated with hypocalcaemia and to maintain a normal serum calcium level. Nine patients were female with a mean age of 48.5 years. A mean of 1.4 parathyroid glands were autotransplanted and the mean PTH level was 3.95 pmol/L. CONCLUSION: This study demonstrates that in a small group of patients following total thyroidectomy, re-vascularization of parathyroid cells may be partial, with inadequate parathyroid reserve to avoid symptoms despite measurable PTH levels. This disorder of partial hypoparathyroidism has not been previously described and represents a small but important complication of total thyroidectomy.