Withdrawal of alfacalcidol supplements following thyroidectomy: baseline plasma PTH predicts successful outcome
M Morris & P Perros
Permanent hypoparathyroidism is rare after total thyroidectomy. However, our experience is that often patients remain on alfacalcidol and calcium supplements long-term after thyroidectomy.
A study was initiated in our centre in 2004, whereby all patients on alfacalcidol or calcium supplements post thyroidectomy underwent a gradual alfacalcidol and calcium reduction programme. Of 57 patients thus enrolled, we report on 22 who were initially on alfacalcidol and had a minimum follow-up of 3 months (). There were 4 men and 18 women, 6 had benign and 16 malignant thyroid pathology. Median age was 45.5 years (range 1990). Median interval since thyroidectomy was 76.4 months (range 19552). Ten patients were able to come off alfacalcidol during a median follow-up of 13.5 months (range 321).
Age, sex, thyroid pathology, time since thyroidectomy, and corrected serum calcium concentration at entry did not correlate with ability to come off alfacalcidol supplements. A lower dose of alfacalcidol (0.67±0.27 vs 1.23±0.16 mcg daily) and a higher plasma PTH (26.1±16.1 vs 8.9±4.7 ng/l) at enrolment correlated with ability to withdraw alfacalcidol (P<0.05). A plasma PTH greater than 18 ng/l was associated with 66.7% sensitivity and 92.3% specificity and 100% positive predictive value.
Withdrawal of alfacalcidol should be attempted post thyroidectomy regardless of duration of treatment and is more likely to be successful in patients on small doses of alfacalcidol and plasma PTH above 18 ng/l.