Preoperative Vitamin D Deficiency Is a Risk Factor for Postsurgical Hypoparathyroidism

• Clin Thyroidol 2021;33:137–139.
• Background
  • Hypoparathyroidism is a rare condition characterized by:
    • Absent or inappropriately low parathyroid hormone (PTH):
      • Resulting in hypocalcemia and hyperphosphatemia
  • The most common cause of hypoparathyroidism is:
    • Surgery-associated accidental removal, damage, or devascularization of the para‐ thyroid glands:
      • Accounting for up to 7.6% of thyroid surgeries
  • This cause of hypoparathyroidism can be divided into:
    • Transient:
      • Which resolves within 6 months after anterior neck surgery (75% of cases)
    • Permanent (chronic):
      • Which persists for ≥ 6 months after the surgery (25% of cases)
  • Several risk factors have been identified, including:
    • Total thyroidectomy
    • Substernal goiter localization
    • Lymph node dissection
    • Inexperienced surgeons
    • Previous neck surgery
    • Malabsorptive states
  • This systematic review and meta-analysis aimed to synthesize the best available evidence between the association of vitamin D deficiency and the risk of transient or permanent postsurgical hypoparathyroidism in patients who undergo thyroidectomy
• Methods
  • This was a systematic review with meta-analysis limited to observational studies that follow the:
    • MOOSE (Meta-analyses Of Observational Studies in Epidemiology) guidelines
  • The inclusion criteria were:
    • Studies investigating the association of preoperative serum vitamin D (25-OHD) levels with the risk of postoperative hypoparathyroidism in patients who underwent thyroidectomy (whether partial or total)
  • A comprehensive literature search was conducted in MEDLINE (PubMed), Cochrane (CENTRAL), and Scopus to include all studies up to October 31, 2020
  • Additionally, gray literature was searched using the most relevant websites, and references in all selected studies were manually searched to identify additional eligible trials
  • Language of publication was restricted to English
  • Two investigators independently completed the primary search and extracted the data
  • For any discrepancies, a third researcher resolved the differences
  • The Newcastle–Ottawa scale was used for assessing the studies’ quality
  • Sensitivity and subgroup analysis were used to investigate confounding factors such as preoperative use of vitamin D and / or calcium supplements, thyroid pathology, type of surgery and surgeon’s volume, quality of studies, and study design
• Results
  • All the studies included in this systematic review were published between 2009 and 2020
  • The qualitative analysis included 56 studies and the quantitative analysis 39 (22 prospective and 17 retro‐ spective)
  • A total of 755,585 participants (607,077 women) were analyzed
  • The sample size for each study ranged from 30 to 620,744 patients
  • Post-thyroidectomy patients with vitamin D deficiency (serum 25-OHD levels ≤ 20 ng/ml) or insufficiency (levels between 21 and 30 ng/ml) showed:
    • A higher risk of developing transient hypoparathyroidism:
      • As compared with patients with preoperative vitamin D sufficiency (serum 25-OHD levels > 30 ng/ml):
        • With high relative heterogeneity among studies (RR, 1.92; 95% CI, 1.50–2.45; I2, 85%)
      • These results remained statistically significant regardless of whether patients had mild (serum 25-OHD levels between 11 and 20 ng/ml [RR, 1.46; 95% CI, 1.10–1.94]) or severe (levels ≤ 10 ng/ml [RR, 1.98; 95% CI, 1.42–2.76]) vitamin D deficiency
  • Regarding permanent hypoparathyroidism:
    • There was an increased risk only in those with severe vitamin D deficiency (RR, 2.45; 95% CI, 1.30–4.63)
  • No differences were found in the subgroup analyses according to the type of study design or quality assessment
• Conclusions
  • In this systematic review and meta-analysis, patients who underwent partial or total thyroidectomy and who had preoperative mild vitamin D deficiency or insufficiency were at increased risk for the development of transient postsurgical hypoparathyroidism
  • Furthermore, those with severe vitamin D deficiency are at increased risk for permanent hypoparathyroidism

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