Learning disabilities and poor motivation to achieve due to prolonged iodine deficiency

Am J Clin Nutr. 1996 May;63(5):782-6. doi: 10.1093/ajcn/63.5.782.


The effect of prolonged iodine deficiency on learning and motivation was studied. One hundred male children--matched for age, socioeconomic status, and formal education--were selected from both severely iodine-deficient (SID) and mildly iodine-deficient (MID) villages. Mean urinary iodine excretion was significantly lower in the SID than in the MID group (219.84 +/- 57.52 compared with 449.14 +/- 32.31 nmol/L, P < 0.001). The serum thyroxine concentration was significantly lower (90.36 +/- 6.46 compared with 123.70 +/- 15.42 nmol/L, P< 0.001) and serum thyroid-stimulating hormone (TSH) was significantly higher in the SID group than in the MID group (6.23 +/- 0.34 compared with 4.85 +/- 0.28 mU/L, P< 0.01). The children were administered maze, verbal, and pictorial learning tasks and a test of motivation. The results showed that SID children are slow learners compared with MID children. In both groups the rate of learning over trials was superior in younger (aged 9-12 y) children although the initial performance of older (aged 12-15 y) children was better (P < 0.01). SID children scored significantly lower than MID children on the achievement motivation scale (P < 0.01). The results are suggestive of neural impairment as well as poor sociopsychologic stimulation, resulting in learning disability and lowered achievement motivation. Unless iodine nutrition is improved in the community as a whole, these abnormalities may prevent millions of children from the SID areas from achieving their full potential even if learning opportunities are made available to them.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Achievement
  • Adolescent
  • Aging / metabolism
  • Child
  • Educational Status
  • Goiter, Endemic / blood
  • Goiter, Endemic / complications
  • Goiter, Endemic / epidemiology
  • Humans
  • India / epidemiology
  • Intelligence
  • Iodine / blood
  • Iodine / deficiency*
  • Iodine / physiology
  • Learning Disabilities / etiology*
  • Learning Disabilities / metabolism
  • Learning Disabilities / physiopathology
  • Learning*
  • Male
  • Maze Learning
  • Motivation*
  • Severity of Illness Index
  • Social Class
  • Thyrotropin / blood
  • Thyroxine / blood
  • Time Factors
  • Verbal Learning


  • Thyrotropin
  • Iodine
  • Thyroxine