Long-term study of serum calcium changes following goitre resection.

Levels of corrected serum calcium, serum free thyroxine index, and serum thyroid stimulating hormone were measured prior to thyroid surgery and 3, 6, 12, 24, and 36 months postoperatively in 18 patients with nontoxic uninodular goitre and in 32 patients with nontoxic multinodular goitre. Additionally, the corrected serum calcium was also determined on the fourth day of surgery. In the former group unilateral resection was done, whilst the latter group had bilateral resection of the thyroid gland. In both goitrous groups, the study demonstrated a slight lowering, albeit significant, of the corrected serum calcium level postoperatively. However, during the study period the mean level of serum calcium was within reference range. Remarkably, there was no significant difference as to change in calcium levels between the two surgical groups. The calcium disturbances were not related to postsurgical thyroid function. Other possible explanations to the change in serum calcium level are discussed, but no responsible mechanism was clarified in the study. It is concluded that although a significant lowering of serum calcium levels takes place after goitre resection, the changes seem not to indicate any therapeutic measures in the long run.