Contributing Factors of Hypothyroidism- A Systematic Review

Introduction: Hypothyroidism is an emerging public health concern, which need to be of due significance. Inspite of iodine supplementation started three decades ago, hypothyroidism is still a problem to be tackled. Apart from iodine deficiency, the contributing factors of hypothyroidism have to explored.

Aim: To identify the contributing factors of hypothyroidism in adults.

Materials and Methods: A systematic literature search was done using PubMed, MEDLINE, Embase, Google Scholar and the internet search from 2000 to 2018. The key words used were hypothyroidism, thyroid disorders, underactive thyroid, contributing factors, causes and associative factors. All the articles were analysed and the data were extracted using eligibility (inclusion and exclusion criteria) criteria. A total of 14 articles, which are either review articles or systematic reviews, in English language, and are fully retrievable were analysed and a systematic review was performed. Among the reviews, nine were review analysis and five were systematic reviews. The risk of bias assessment was done at the study level and data synthesis was done based on the criteria satisfied by the checklist.

Results: The present analysis has included studies related to contributing factors of hypothyroidism. The analysis revealed the following contributing factors of hypothyroidism. Too little or too much iodine (43%), excess fluoride (7%), female gender (14%), presence Thyroid Per Oxidise (TPO) antibodies (36%), smoking status (14%), age above 70 years (21%), unregulated use of pesticides (14%), contaminated drinking water (14%), certain medicines (29%), use of plastic bottles contain Bisphenol A (BPA) and paper cups insulated with plastics (7%) and exposure to goitrogens (7%).

Conclusion: Hypothyroidism is a leading emerging health problem in India. The prevalence is 11-15%. Despite the fact iodine fortification since 1983, hypothyroidism is a major public health to be tackled. In the current review five studies from India were included. Most of the studies showed the iodine as the contributing factor either in too much level or too little level.