Agencies and Organizations Involved with International Health

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Iodine Deficiency Disorders
NUTR 600/ HSERV 590
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Iodine Deficiency Disorders

• The single most preventable cause of mental
  retardation and brain damage in the world
• Control programs are in place in most countries
  of the world, primarily through salt iodization
• Scientific data are required to demonstrate that
  adequate amounts of iodine are reaching the
  target population and having an impact.
• However, there has been a lack of clarity in
  indicators (and criteria) for tracking progress

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Iodine Deficiency Disorders

• World Health Assembly (1990) adopted the goal of
  the elimination of IDD as a public health problem
  by the year 2000
• Progress towards the elimination of IDD can only
  be demonstrated if it is measured
• This requires the selection of appropriate
  indicators of both process and impact

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Causes of Iodine Deficiency
Snow
Atmosphere
Rain
Iodine is not available in the soil, since it is
washed away by rain and snow, mostly in mountain
areas and plains
Lake
River
Sea
Iodine
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Daily Iodine Requirements
Just a teaspoon in a lifetime
Daily physiological requirements for adults
100-150 ?g Assumed daily per capita salt
consumption 10 grams Fortification level of
elemental iodine 15 ppm
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Spectrum of Iodine Deficiency Disorders
Fetus Abortion Still Birth Congenital
Anomalies Increased Perinatal and Infant
Mortality Cretinism (Neurological and
Myxedematous)

• Neonatal Neonatal Hypothyroidism

Childhood Impaired mental and physical
development
Adult Complications of Goiter Iodine-induced
hyperthyroidism (IIH)
All ages Goiter Hypothyroidism
NUTR 600/ HSERV 590
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Population with Iodine Deficiency
At risk of mental impairment 1.6 billion
WHO (1999)
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Population with Iodine Deficiency
Goitre 655 million
At risk of mental impairment 1.6 billion
WHO (1999)
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Population with Iodine Deficiency
Brain damage 26 million
Goitre 655 million
At risk of mental impairment 1.6 billion
WHO (1999)
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Population with Iodine Deficiency
Cretinism 6 million
Brain damage 26 million
Goitre 655 million
At risk of mental impairment 1.6 billion
WHO (1999)
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Population with Iodine Deficiency
Cretinism
Brain damage
Goitre
At risk of mental impairment 1.6 billion
WHO (1999)
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Population with Iodine Deficiency
Cretinism
Brain damage
Goitre
At risk of mental impairment 1.6 billion
WHO (1999)
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Function of the Thyroid Hormones
Brain
Pituitary
TSH
Thyroid gland
Thyroid
hormones
Muscle
Heart
Kidneys
Liver
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Enlargement of thyroid gland
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Indicators of IDD in a Population

• Process of adequately iodized salt at
  production level
• of adequately iodized salt at household level
• of iodized salt at household level
• Impact Goiter
• Urinary iodine excretion (UIE)
• Thyroid hormones

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Indicators of IDD - Process

• Salt iodine levels
• Two methods
• Rapid test kits (semi-quantitative)
• Titration
• Salt monitoring systems
• Ensure adequate iodine levels at all points of
  distribution from Production to Household
• Where problems are identified, take corrective
  action

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Indicators of IDD - Impact

• Goiter
• Total goiter prevalence
• Grade 0 No palpable or visible goiter
• Grade 1 Palpable goiter
• Grade 2 Visible goiter
• Urinary iodine excretion (UIE)
• Best marker of recent dietary intake of iodine
• Most iodine absorbed in the body eventually
  appears in urine

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Indicators of IDD - TGR

• Total Goiter prevalence
• WHO, UNICEF, ICCIDD (2001)
• Prevalence Significance of Public Health Problem
• lt 5 No IDD
• 5-19.9 Mild IDD
• 20-29.9 Moderate IDD
• ? 30 Severe IDD

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Iodine Deficiency - Goiter
Visible goiters pretty easy to diagnose
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Iodine Deficiency - Goiter
Palpable goiters are much more problematic

• WHO revised criteria for palpable goiter
• 1960 lobes larger than ends of thumbs
• 1994 an enlarged thyroid that is palpable, but
  not visible
• In Tanzania, change in clinical definition led to
  a 25 increase in the prevalence of palpable
  goiter
• Comparability may become problematic and lead to
  smaller decreases over time, or actual increase
  in goiter in spite of IDD control efforts

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Assessment of Enlarged Thyroid

• Clinical observation of the thyroid by palpation
  has been the conventional method to assess goiter
• Ultrasound (U/S) has become more widely used to
  provide a more precise measurement of thyroid
  volume.
• U/S is particularly important when the prevalence
  of visible goiters is low
• Problem with U/S is the lack of normative
  reference data (from iodine replete population)

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Inter-observer variation in palpation

• The sensitivity and specificity of palpation are
  low, particularly in grades 0 and 1 due to high
  inter-observer variation.
• In studies of trained endocrinologists, there is
  as much as 30-40 disagreement in the
  classification with ? lt 0.40

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Correspondence Between U/S and Palpation - Nepal

• As part of National MN Survey
• Sub-sample of 403 SAC (8-10 years of age)
• U/S measured by single trained examiner (gold
  standard) using a SonoAce 600 portable U/S
  machine
• Palpation performed by field teams
• Thyroid volume calculated based on measurements
  of the width, depth and length using standard
  formula
• Thyroid volume compared to standard thyroid
  volume-for-age values and dichotomised normal
  (lt 97th centile) and enlarged (gt 97th centile)

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Correspondence Between U/S and Palpation - Nepal
PVP 28.3 PVN 83.2 Se 69.1 Sp 46.6
Gorstein (2001)
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Indicators of IDD - UIE

• Population IDD Status
• WHO, UNICEF, ICCIDD (2001)
• Median value Iodine Status
• lt 20 ?g/l Severe iodine deficiency
• 20-49 Moderate iodine deficiency
• 50-99 Mild iodine deficiency
• 100-199 Ideal iodine intake
• 200-299 More than adequate intake (may pose
  risk of IIH)
• ? 300 Excessive iodine intake
• In populations with longstanding iodine
  deficiency and rapid improvement in iodine
  intake, median values above 200 ?g/l are not
  recommended

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IDD IndicatorsDepends on the status of control
program

• It is now accepted that thyroid volume is less
  useful in assessing current IDD status during
  implementation of USI and soon after achieving
  USI
• Prior to any intervention, the prevalence of low
  UI and goiter will be in agreement with each
  other indicating IDD
• Once USI is phased in (over months or years), the
  prevalence of low UI will fall faster than the
  prevalence of goiter

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Appropriateness of IDD IndicatorsDepends on
control program status
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Changes in IDD IndicatorsChina clinical trial,
Jiangsu Province

• IDD endemic area
• Households provided with iodised salt at 25 ppm
• Baseline and follow-up at 6,9,12 and 18 months
  after initiation of intervention
• At baseline, the severity of IDD was mild (based
  on UIE) and moderate (based on TGR and U/S)
• After six months, UIE had increased to adequate
  levels, while thyroid size measures still
  indicated moderate IDD
• After 18 months, all three measures indicated
  adequate iodine status

Sullivan, et. al., 2001
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IDD IndicatorsDepends on the status of control
program

• Just as it takes years for goiter to develop in
  school children, it takes years for the thyroid
  to return to normal size after iodine
  sufficiency is achieved
• The amount of time it takes for the UI and
  thyroid size to be in agreement will depend on
  the severity of IDD at baseline and the length of
  time it takes to phase in the USI program

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Correspondence between Indicators
UNICEF, 1997
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Criteria for IDD Elimination - 2000
WHO, UNICEF ICCIDD (2001)
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Implications

• Urinary iodine is responsive to improvements in
  iodine intake
• However, the criteria for adequacy of USI
  programs may be too rigid and does not take into
  account differences in salt consumption
• In many developing countries (including Nepal),
  more than 10 grams of salt are consumed per day
  and therefore lower levels of iodine in salt
  (ppm) may be necessary

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Control of IDD through Universal Salt Iodisation
(USI)

• Today
• Some 70 per cent of households in the developing
  world are using iodized salt, compared to less
  than 20 per cent at the beginning of the decade.
  
• As a result, 91 million newborns are protected
  yearly from significant loss in learning ability

• Unfinished Business
• There are still 35 countries where less than half
  the households consume iodized salt

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Coverage of Iodized Salt by Region
Source UNICEF (2002)
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Levels of Iodized Salt Coverage
90 or more
50 to 89

Less than 50
Source UNICEF (2002)
No recent data
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Major Increases in Iodized Salt Coverage
Source UNICEF (2004)
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41 Million Newborns Still Unprotected from
Learning Disabilities
Source UNICEF (2002)