Endocrine Abstracts

Background: Post-operative hypocalcaemia affects up to 30% of patients. It may be delayed to the second or third post-operative day and is therefore the key determinant of post-operative stay. Various strategies have been used to overcome this problem including the blanket administration of calcium and discharge followed by daily blood tests.

Objectives: To evaluate the use of using a parathyroid hormone (PTH) assay 4 h following surgery as a predictor of post-thyroidectomy hypocalcaemia and therefore of safe early discharge.

Methods: A review of 97 patients undergoing thyroidectomy between October 2005 and March 2007 was performed. All patients had PTH measurements performed 4 h following surgery and serum calcium estimations performed on day 1 and day 2 following surgery and again at out patient follow up. Post-operative hypocalcaemia was classified as a serum calcium <2.00 mmol/l and permanent hypoparathyroidism was classified as a serum calcium <2.15 mmol/l 3 months after surgery. The sensitivity and specificity of PTH as a predictor of post-operative hypocalcaemia was calculated.

Results: Twenty patients developed hypocalcemia (20.6%), and one patient (1%) had permanent hypoparathyroidism. Four-hour post-operative PTH levels were reduced in the hypocalcemic patients compared to normocalcemic patients (2.6±2.2 vs 3.9±2.1 pmol/l) (P<0.016). A significant association existed between low PTH levels and the occurrence of hypocalcemia (P<0.004). Whilst in 69 patients who remained normocalcemic a normal PTH predicted this, 8 normocalcaemic patients also had a low PTH. The sensitivity, specificity, positive and negative predictive value of PTH was 40, 89.6, 50 and 85.1% respectively.

Conclusions: Post-operative PTH measurement at 4 h is a useful predictor of normocalcaemia following surgery but remains a suboptimal predictor of post-thyroidectomy hypocalcaemia and permanent hypoparathyroidism. Further studies are required to establish the ideal timing and potential role for this tool in predicting post-operative hypocalcaemia and shortening hospital stay.