• Credits

  • Section Writer: Dr. Om J Lakhani
  • Section Editor: Dr. Om J Lakhani

• Q. What are dietary sources of Iodine?

  • Seafood
  • Iodized salt
  • Veggies are grown in iodine-rich soil
  • Cow’s milk

• Q. Summarize the consequences of Iodine deficiency?

  • Goiter
  • Hypothyroidism
  • Cretinism- Neurological cretinism , myxedemoatous cretinism
  • Neonatal and infant mortality
  • Subclinical neurological deficit
  • Intellectual disability

• Q. Which form of Iodine is present in food?

  • Iodide

• Q. What is the recommended iodine intake by IOM?

  • 0-6 months infant – 110 mcg
  • 7-12 months- 130 mcg
  • 1 – 8 years- 90 mcg
  • 9-13 years- 120 mcg
  • Adolescent and adults – 150 mcg
  • Pregnancy – 220 mcg
  • Lactation – 290 mcg

• Q. Describe the severity of iodine deficincy based on urinary iodine levels ?

  • Urinary iodine
    • More than 100 mcg/l- normal
    • 50-99 mcg/l – mild deficiency
    • 20-49 mcg/l- moderate
    • <20 mcg/l- severe

• Q. What is the normal urinary iodide concentration in pregnancy?

  • 150-250 mcg/l
  • So in pregnancy - <150 mcg/l – is low

• Q. What type of goiters are seen due to iodine deficiency?

  • Diffuse goiter- children
  • MNG – adult
  • Thyroid nodules- increase risk of follicular neoplasm

• Q. Give the timing of thyroid hormone production in the fetus?

  • 0-12 weeks- fetus dependent on maternal thyroid
  • 10-12 weeks- TSH appears
  • 12 week- thyroid hormone production starts, but it is of limited quantity
  • 18 weeks- adequate production of the thyroid by the fetus

• Q. How much IQ is lost due to maternal iodine deficiency?

  • 13.5 points

• Q. What are the means of evaluating the iodine status of the population?

  • Urinary iodide concentration- current iodine status
  • Serum Thyrogliobulin in infants and children
  • Neonatal TSH
  • Goiter
  • Thyroid volume

• Q. How much Iodine is present in iodized salt?

  • 45-80 mcg/gram of salt

• Q. What form of Iodine is present in salt?

  • Potassium iodide
  • Potassium iodate in tropical countries

• Q. What agent is used to correct severe iodine deficiency in pregnant women?

  • Lipidol
  • This is a radiocontrast agent
  • 0.5- 1 ml single dose- provides Iodine for 6 month- 1 year
  • IM injection – provides for 2-3 years

• Q. What are the adverse effects of iodine supplementation?

  • hyperthyroidism- those are having pre-existing nodular goiter- Jod Badeshow effect
  • Hypothyroidism – those having the existing autoimmune disease of thyroid – failure to escape from Wolf Chiakoff effect

• Q. What is Wolf-Chiakoff effect ?

  • Wolf-Chaikoff (WC) effect: Excess iodide blocks oxidation and organification of Thyroglobulin
  • Escape from WC effect: However, within 48-72 hours, there is a reduction of iodide uptake by downregulation of NIS. This is an escape from Wolf Chiakoff.
  • This often fails in patients with an autoimmune disease, which leads to hypothyroidism

• Q. What minimal dose of iodide is required to produce the Wolf-Chaikoff (WC) effect ?

  • A dose of atleast 2000 mcg per day of iodide is required to produce the Wolf-Chaikoff (WC) effect

• Q. What specific systems in the thyroid hormone metabolism is inhibited by the iodide in the Wolf-Chaikoff (WC) effect ?

  • The oxidation and organification of the thyroglobulin are inhibited by the Wolf-Chaikoff (WC) effect

• Q. Iodide is used for treatment of thyroid storm and preparing a patient for thyroid surgery. Is the Wolf-Chaikoff (WC) effect exploited here ?

  • No
  • The phenomenon here is a little different
  • In Preoperative use of iodide or use of the same in thyroid storm, iodide acts by inhibiting the proteolysis of thyroglobulin
  • The above prevents the release of the thyroid hormone
  • However, this effect is also short lasting and last for 5-7 days.
  • After this period, the impact is lost and this is called "iodide escape"

• Q. Why does the iodide escape take place ?

  • Inhibition of proteolysis of thyroglobulin, reduces the circulating thyroid hormones
  • This stimulates the TSH release which then restores the proteolysis of the thyroglobulin leading to the escape of this effect.

• Q. What is the difference between iodide escape and escape from Wolf-Chaikoff (WC) effect ?

  • A thyroid gland with underlying disease (underlying autoimmunity) can show the iodide escape, but may not be able to escape from the a Wolf-Chaikoff (WC) effect
  • A healthy thyroid gland can escape from both the Wolf-Chaikoff (WC) effect as well as the iodide escape

• Q. What is Jod-Badeshow phenomenon ?

  • This is a development of hyperthyroidism following iodine intake
  • This typically occurs in people who are predisposed to the same for example those having a multinodular goiter, subclinical Graves' disease etc
  • Patients having thyroid autonomy go on to develop hyperthyroidism because iodine add "fuel to fire"
  • Some people believe that such a phenomenon is seen in areas of iodine deficiency where the hyperthyroidism remains subclinical or does not manifest because of lack of adequate iodine required for synthesis of thyroid hormone. When iodine is provided in such a scenario, the unmasking of the hyperthyroidism takes place
  • This phenomenon can also be triggered by Iodinated contrast agents

• Q. What is the upper limit of daily iodine intake?

  • Adults- 600-1100 mcg/day
  • Adolescent – 500-900 mcg
  • Children – 200-450 mcg

• Q. Give the Indian data on iodine status?

  • Mean UIC- 153 mcg/l – Iodine sufficiency
  • 70% of household receive iodized salt

• Q. Where was the first successful trial of Iodine replacement in India?

  • Kangra valley in Himachal

• Q. What is the govt program for iodine deficiency?

  • National Iodine Deficiency Disorders Control Programme

• Q. What is the recommended iodine level of salt in India?

  • At production – 30 ppm
  • At consumption – 15 ppm

• Q. How does iodized and non-iodized salt appear?

  • Iodized salt – appears white
  • Non-iodized salt –appears yellow

• Q.  What care must be taken to preserve Iodine in salt?

  • Don’t use salt one month after opening
  • Don’t store for more than six months
  • Add salt after cooking
  • Keep salt in a vacuum-sealed container
  • Not stored near the stove

• Q. Give the various disorder of iodine deficiency based on the age of a person?

  • Fetal / perinatal
    • Neurological cretinism
    • Myxedematous cretinism
    • Increase perinatal mortality
    • Abortion and stillbirth
    • Congenital anomalies
  • Neonate / infant
    • Neonatal hypothyroidism
    • Increase neonatal and infant mortality
    • Delayed milestones
    • Neonatal goiter
  • Child and Adolescent
    • Juvenile hypothyroidism
    • Mental retardation
    • Short stature
    • Diffuse goiter
  • Adult
    • Hypothyroidism
    • Pregnant women- the risk of complication in the fetus
    • Multinodular goiter
    • Follicular carcinoma of thyroid

• Q. What is the WHO grading of the goiter?

  • Grade 0- no goiter
  • Grade 1 – palpable, not visible
    • 1a- palpable with the neck in neutral
    • 1b- palpable with neck extended
  • Grade 2- visible and palpable

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