Does iodine excess lead to hypothyroidism? Evidence from a case-control study in India.

Journal Article (Journal Article)


Iodine deficiency disorders have been known to mankind since antiquity and various researchers elucidated the role of iodine in its causation. However, recent evidence shows that the entire control program ignored multi-causality and association of increased iodine intake with hypothyroidism. This study was conducted to assess differences of iodine intake as measured by urinary iodine excretion (UIE) between cases of hypothyroidism and healthy controls.


A case-control study was conducted with three groups (cases, hospital controls and community controls) in two cities of India. Patients with overt hypothyroidism were cases (n = 150) and were compared with age, sex and socioeconomic status-matched hospital (n = 154) and community (n = 488) controls. Thyroid function tests (T3, T4, TSH) were used as diagnostic and inclusion criteria. TPOAb and UIE estimation were carried out for all study participants.


Mean values of TPOAb and UIE were higher in cases as compared to hospital controls as well as community controls (p <0.05). With a cut off of 34 IU/mL for TPOAb, more cases had an anti-TPO level >34 as compared to hospital controls (p <0.001) as well as community controls (p <0.001); OR, 0.06 (95% CI, 0.03, 0.12) and 0.08 (0.05, 0.12), respectively. For UIE cut-off of 300 μg/L, more cases than hospital controls (p = 0.090) and community controls (p = 0.001) had higher levels; OR, 0.671, (0.422, 1.066) and 0.509, (0.348, 0.744), respectively.


The study has clearly shown that cases of hypothyroidism are associated with excess iodine intake. Cohort studies to generate further evidence and an eco-social epidemiological approach have been suggested as the way forward.

Full Text

Duke Authors

Cited Authors

  • Kotwal, A; Kotwal, J; Prakash, R; Kotwal, N

Published Date

  • August 2015

Published In

Volume / Issue

  • 46 / 6

Start / End Page

  • 490 - 494

PubMed ID

  • 26247626

Electronic International Standard Serial Number (EISSN)

  • 1873-5487

International Standard Serial Number (ISSN)

  • 0188-4409

Digital Object Identifier (DOI)

  • 10.1016/j.arcmed.2015.07.005


  • eng