Endocrine Abstracts (2013) 32 P123 | DOI: 10.1530/endoabs.32.P123

Early measure of postoperative iPTH and corrected calcium as predictors of future hypoparathyroidism: which, when and why?

Miguel Paja, Cristina Moreno, Estíbaliz Ugarte, Amelia Oleaga, Ma Teresa Gutiérreza, Ana J Izuzquiza, Eider Etxeberría, Natalia C Iglesias, Aitzol Lizarraga & María P Martínez-Mate

Hospital de Basurto, Bilbao, Basque Country, Spain.

Introduction: Intraoperative parathyroid hormone assay (ioPTH) has been validated as a useful tool for predicting postoperative hypocalcaemia (hypoCa) after thyroid surgery and has been proposed as a guide to early discharge from hospital. Its value to predict the risk of future hypoparathyroidism (hypoPT) has not been analyzed in detail. We evaluate this role in our recent surgical series.

Description of methods/design: Patients with total thyroidectomy from 2005 to 2011, evaluated more than 1 year after surgery. Permanent hypoPT (PhypoPT) was defined by (iPTH)<15 pg/ml without treatment 1 year after surgery. Cases with spontaneous recovering of parathyroid function after a period of (iPTH) <15 were named as transient hypoPT (ThypoPT). We analyze the correlation between (iPTH) measured 24 h after surgery (iPTH24 h) and future parathyroid function. We also analyze the correlation between (iPTH) measured immediately (1–3 h) after surgery (iPTH1–3 h), corrected calcium monitored 6 h postoperatively (Ca6 h) and subsequent parathyroid status.

Results: 502 patients had (iPTH24 h), 305 of them also had (iPTH1–3 h). Of 125 with (iPTH24 h) <3 pg/ml, 40 presented PhypoT. The remainders were transient forms, 56% corrected in the 1st month after surgery. Mean (S.D.) (iPTH24 h) in patients without hypoPT was 39.13 (23.45) vs 3.54 (3.54) in patients with hypoPT (P<0.0001). Mean (S.D.) (iPTH1–3 h) was 34.88 (28.02) and 3.10 (7.9) pg/ml (P<0.0001) respectively. Median (iPTH24 h) and (iPTH1–3 h) in patients without hypoPT were 33.5 and 30 pg/ml (P<0.001). Postoperative hypoCa, defined as corrected plasmatic calcium <7.5 mg/dl, presented in 183/647 patients including 66.3% of patients with (iPTH24 h) <10 pg/ml, vs 10.9% of them with (iPTH24 h) ≥10 pg/ml (OR: 3.48 (CI: 2.6–4.64)). The OR for postoperative hypoCa with (iPTH1–3 h) <10 pg/ml was 3.89 (CI: 2.48–6.10). (iPTH24 h) >15 pg/ml was present in 5% of patients with hypoPTH and (iPTH1–3 h) >15 pg/ml in 9.5%, all ThypoPT. Mean (Ca6 h) was significantly lower in patients who suffered hypoPT (8.63 vs 8.22; P<0.001).

Conclusion: Our study confirms the utility of perioperative (PTH) as predictor of postoperative hypoCa and future hypoPT, but we have not found an exact level or timing for its measurement.