Background: British Association of Thyroid and Endocrine Surgeons defines post-operative hypocalcaemia as adjusted calcium of < 2.0 mmol/l; late hypocalcaemia as the ongoing requirement for calcium/Vitamin D supplements at 6 months; permanent post-surgical hypoparathyroidism (PSHP) at 12 months. The incidence rates of late hypocalcaemia are 6.512.1% and PSHP is 0.9%4.5%.
Objective: To evaluate PSHP incidence rate in total thyroidectomy patients beyond 12 months post-operative period.
Methods: A list of consecutive total thyroidectomy cases was obtained from Histopathology department from 2010 to 2017 and retrospective evaluation of electronic records was undertaken. Adjusted calcium recorded at least 12-months post-operative period was considered.
Results: Over 8-year period, Out of 507, n=201 patients had total thyroidectomy; rest excluded due to lack of data or erroneous coding. n=58 post-operative hypocalcaemia (incidence 28.9%); n= 21 (19F:2M)(incidence 10.4%) developed PSHP; mean follow-up 6.02 years. At diagnosis: Mean age 48-years; mean BMI 27.7 wt/ht2; mean adjusted calcium 1.84 mmol/l (2.102.60); mean Parathormone 1.23 pmol/l (47); mean Vitamin-D 42 pmol/l (>50 is normal). 94%(19/21) treated with Vitamin D analogues (86% alfacalcidiol, 8% calcitriol) with or without calcium salts.
Discussion: Our retrospective analysis identified higher incidence rate of permanent PSHP (10.4%) similar to 2012 BAETS national audit (12.1%). Temporary hypocalcaemia incidence (28.9%) was similar to majority of studies (2346%). Female sex, extended neck dissection, post-operative iodine ablation in thyroid cancer was identified as risk factors for PSHP. >60% had not had calcium level checked after 12 months and therefore unable to ascertain current calcium status.
Learning point: We feel that the incidence rates of permanent PSHP is higher than quoted in literature. Missed diagnosis can result in considerable morbidity and is potentially fatal. Close monitoring of calcium is recommended for a minimum period of 12 months to optimise detection and for timely management.