Iodine is essential for thyroid hormone production and is obtained through foods like seaweed and seafood or iodized salt. Iodine deficiency can cause goiter and irreversible intellectual and growth impairments while excess iodine can inhibit the thyroid. Various indicators are used to assess iodine status including urinary iodine and thyroid size. Iodine interacts with medications for hyperthyroidism and high blood pressure and deficiencies in selenium or vitamins A, E, zinc and iron can exacerbate effects of iodine deficiency.

1. UNIVERSITY PUTRA MALAYSIA
FACULTY OF MEDICINE AND HEALTH SCIENCES
DEPARTMENT OF NUTRITION SCIENCES
IODINE
By
Mohammed Ellulu
MICRONUTRIENTS IN HEALTH AND DISEASE

2. Introduction
 In 1896, Baumann determined the association of
iodine with the thyroid gland.
 In 1914 Kendall, with revisions by Harrington in
1926, described the hormone complexes
synthesized by the thyroid gland using iodine that
are so integral to human growth and development.
 Recent work has demonstrated iodine, involved
through peroxidases in enzymatic activity and
production of numerous active metabolites in the
human body.
2

3. Absorption, Transport, and Storage
 Iodine is usually ingested as an iodide or iodate
compound and is rapidly absorbed in the intestine.
 Iodine entering the circulation is actively trapped by the
thyroid gland.
 The active transport of iodine is likely to be based on
cotransport of sodium and iodine in capillaries.
 Anion thiocyanate inhibits the active transport.
 In addition to trapping iodine in thyroid cells, follicular
cells also synthesize the glycoprotein, thyroglobulin (Tg),
from carbohydrates and amino acids (including tyrosine)
obtained from the circulation.
3

4.  Thyroglobulin moves into the lumen of the follicle
where it becomes available for hormone production.
 Thyroid peroxidase (TPO), a membrane-bound
hem-containing glycoprotein, catalyzes the
oxidation of the iodide to its active form, I2, and
the binding of this active form to the tyrosine in
thyroglobulin to form mono- or diiodotyrosine (MIT
or DIT).
 These in turn combine to form the thyroid hormones
triiodothyronine (T3) and thyroxine (T4).
Absorption, Transport, and Storage
4

5. Tyrosine and Thyroxine (T4)
5

6. Thyroid gland
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7. Recommended Intakes
Table 1: Recommended Dietary Allowances (RDAs) for Iodine
Age Male Female Pregnancy Lactation
Birth to 6 months 110 mcg* 110 mcg* (* Adequate intake)
7–12 months 130 mcg* 130 mcg*
1–3 years 90 mcg 90 mcg
4–8 years 90 mcg 90 mcg
9–13 years 120 mcg 120 mcg
14–18 years 150 mcg 150 mcg 220 mcg 290 mcg
19+ years 150 mcg 150 mcg 220 mcg 290 mcg
7

8. Sources of Iodine
Food
 Seaweed (such as kelp), seafood, dairy products.
Ionized-Salt
 More than 70 countries, including the United States
and Canada, have salt iodization programs.
 FDA approved potassium iodide and cuprous iodide
for salt iodization while the WHO recommends the
use of potassium iodate due to its greater stability.
Supplements
8

9. Iodine Deficiency
 Iodine deficiency has multiple adverse effects on
growth and development, and is the most common
cause of preventable mental retardation in the
world.
 Resulted mainly from inadequate thyroid hormone
production.
 During pregnancy and early infancy, iodine
deficiency can cause irreversible effects.
 Under normal conditions, the body tightly controls
thyroid hormone concentrations via TSH.
9

10.  TSH secretion increases when iodine intake falls below
about 100 mcg/day.
 TSH increases thyroidal iodine uptake from the blood
and the production of thyroid hormone.
 However, very low iodine intakes can reduce thyroid
hormone production even in the presence of elevated
TSH levels.
 If iodine intake falls below approximately 10–20
mcg/day, hypothyroidism occurs.
 Goiter is the earliest clinical sign of iodine deficiency.
Iodine Deficiency
10

11. Iodine Deficiency
 In pregnant women, iodine deficiency can cause major
neurodevelopmental deficits and growth retardation in
the fetus, as well as miscarriage and stillbirth.
 Chronic, severe iodine deficiency in utero causes
cretinism (mental retardation).
 Stunted growth, delayed sexual maturation.
 In infants and children, less severe iodine deficiency can
cause neurodevelopmental deficits such as somewhat
lower-than-average intelligence.
 Mild to moderate maternal iodine deficiency associated
with an increased risk for attention deficit hyperactivity
disorder in children.
11

12. Classification of hypothyroidism
12
3ry
2ry
1ry
4ry

13. Iodine and Health
Fetal and infant development
 During early pregnancy, the fetus depends entirely
on maternal T4 and maternal iodine intake.
 Production of T4 increases by approximately 50%
during pregnancy, requiring a concomitant increase
in maternal iodine intake.
 Breast milk contains iodine, although concentrations
vary based on maternal iodine levels.
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14. Iodine and Health
Fibrocystic breast disease
 Is a benign condition characterized by lumpy,
painful breasts and fibrosis. It affects women of
reproductive age, also occur during menopause,
especially in women taking estrogens.
 Breast tissue has a high concentration of iodine,
especially during pregnancy and lactation.
 Some research suggests that iodine supplementation
might be helpful for fibrocystic breast disease.
14

15. Radiation-induced thyroid cancer
 Thyroidal uptake of radioactive iodine is higher in
people with iodine deficiency than in people with
iodine sufficiency.
 The FDA has approved potassium iodide as a
thyroid-blocking agent to reduce the risk of thyroid
cancer in radiation emergencies involving the
release of radioactive iodine (as nuclear accidents).
Iodine and Health
15

16. Assessment of Iodine Status
 There are several additional indicators that are used to
assess thyroid function, such as T4 and T3, but these are
less accurate in reflecting iodine status since conversion
of T4 to T3 and cellular uptake is so responsive to
peripheral need.
 Urinary iodine reflects iodine sufficiency, and output
decreases with diminished intake.
 Thyroid size, either estimated by palpation or using
ultrasound volume determination, reflects iodine status
since deficiency results in thyroid enlargement, or goitre.
16

17. Assessment of Iodine Status
17
 In adults, where long-standing thyroid enlargement from
iodine deficiency may be minimally responsive to
corrected iodine intake, palpation may be misleading
and could overestimate the current level of iodine
sufficiency.
 TSH is produced in response to decreased iodine intake
and diminished thyroid hormone production and is used
as a measure of iodine status.
 Uptake of radioactive iodine isotopes can be used to
scan the gland, and determine the affinity of the gland
to introduced iodine, and is a measure of deficiency.

18. Iodine interaction
18
Major Highly clinically significant. Avoid combinations; the risk of
the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid
combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk
and consider an alternative drug, take steps to circumvent the
interaction risk and/or institute a monitoring plan.

19. Iodine interaction
19
Medications for an overactive thyroid (Antithyroid
drugs) Interaction Rating Major.
 Taking iodine along with medications for an
overactive thyroid might decrease the thyroid too
much.
 Some of these medications include methimazole,
and potassium iodide.

20. Iodine interaction
20
Amiodarone Interaction Rating: Moderate.
 Amiodarone contains iodine. Taking iodine supplements
along with amiodarone might cause too much iodine in the
blood. Too much iodine in the blood can cause side effects
that affect the thyroid.
Medications for high blood pressure (ACE inhibitors)
Interaction Rating: Moderate.
 Decreases quickly the body gets rid of potassium. Most
iodide supplements contain potassium. Taking potassium
iodide along with some medications for high blood pressure
might cause too much potassium in the body.

21. Iodine interaction
21
 Selenium is required for converting of thyroxine (T4) to
triiodthyronine (T3); the removal of iodine molecule from T4.
 The iodine molecule that is removed gets returned to the
body's pool of iodine and can be reused to make additional
thyroid hormones.
 If body is deficient in selenium, the conversion of T4 to T3 is
slowed, and less iodine is available for the thryoid to use in
making new hormones.
 Animal studies have shown that arsenic interferes with the
uptake of iodine by the thyroid, leading to goiter.
 In addition, dietary deficiency of vitamin A, vitamin E, zinc
and/or iron can exaggerate the effects of iodine deficiency.

22. References
22
 1. National Research Council, Committee to Assess the Health Implications of
Perchlorate Ingestion. Health Implications of Perchlorate Ingestion. Washington, DC:
The National Academies Press, 2005.
 2. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for
Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese,
Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National
Academy Press, 2001.
 3. World Health Organization. United Nations Children's Fund & International
Council for the Control of Iodine Deficiency Disorders. Assessment of iodine
deficiency disorders and monitoring their elimination. 3rd ed. Geneva, Switzerland:
WHO, 2007.
 4. Patrick L. Iodine: deficiency and therapeutic considerations. Altern Med Rev.
2008 Jun;13(2):116-127.
 5. Zimmermann MB. Iodine deficiency. Endocr Rev. 2009 Jun;30(4):376-408.
 6. Zimmermann MB, Jooste PL, Pandav CS. Iodine-deficiency disorders. Lancet.
2008 Oct 4;372(9645): 1251-1262.