Iodine deficiency disorders

Iodine is an essential component in thyroid hormone production

Thyroid hormone regulates basic metabolism :energy consumption, cellular activity, growth and in particular brain development.

Hypothyroidism: slow, cold, sluggish brain function, short stature, mental and motor development delayed or slowed. In extremes general neurological development delayed.

Hormone regulationHypothamalus

TSH T3 T4

Hypofysis

- SomatostatinTSHRF

T4 T3

I pool

Hormones and iodine deficiency

Spectrum of diseaseTable 1. The Spectrum of Iodine Deficiency Disorders, IDD.Fetus Abortions Stillbirths

Congenital anomaliesIncreased perinatal mortalityEndemic cretinism

Neonate Neonatal goiter Neonatal hypothyroidismEndemic mental retardationIncreased susceptibility of the thyroid glandto nuclear radiation

Child and Goiter adolescent (Subclinical) hypothyroidismImpaired mental functionRetarded physical developmentIncreased susceptibility of the thyroid glandto nuclear radiation

Adult Goiter with its complications HypothyroidismImpaired mental functionSpontaneous hyperthyroidism in the elderlyIodine-induced hyperthyroidismIncreased susceptibility of the thyroid glandto nuclear radiation

Adapted from Hetzel (1), Laurberg et al. (52, 171) and Stanbury et al. (158).

Importance of the problem

Prevalence

1 billion persons exposed200 million persons affected (goitres)26 million cases of mental problems6 million cases of cretinism

Goitre

Increase in size four to five times distal phalanx of the thumb

Aesthetic Compression Related hypothyroidism: is not a

compensation cancer Iod Basedow (hyperthyroidism) due to

hyperstimulation, mutation autonomous nodules

Iodine deficiency and the foetus

Brain development fast between 3-5 months pregnancy and from third trimester till end of second year

Maternal T4 essential for first 24 weeksFoetal T4 starts at 24 weeks30% cord blood is of maternal origin

Iodine and the neonate

Perinatal mortalityInfant mortalityLow birth weightBrain development needs T4Iodine deficiency mental retardation,

retarded motor development. General IQ decrease of 15 Points

Iodine deficiency and adults

Lack of energyapathy, slow brainsgoitre and mechanical complicationsNodular thyroidhyperthyroidismPregnancy and cretinism

Aethiology

Low iodine uptake. Soil dependent erosion, wash away: deltas

Goitrogens Manioc: linnamarin thiocyanate

Blocs uptake of Iodine at the thyroid, competitive inhibition

Traditional preparationsKonzo

Brassica family polutants

IDD and selenium deficiency

Se part of peripheral type I de-Iodinase (kidney and liver)

Se deficiency: slower T4 to T3 metabolisation

Se part of Glutathion peroxidase : protector of H2O2 damage Thyroid damage, disfunction of thyroid

Cerebral de-iodinase is not Se dependent Glutathion peroxidase stimulates T4

production

Iodine needs

RECOMMENDED INTAKE ug/day

0 - 6 months 35 8 ug/kg5 ug/100ml of milk7 ug/100 kcal

6 - 12 months 451 - 10 years 60 – 100>= 11 years 100 - 115pregnancy – lactation 125 - 150

Diagnosis of endemicity

Prevalence of goitreDosage of urinary iodineTSH dosagePrevalence of cretinism

Prevalence of goitre

Class Description

0 Absence of goitre

Ia Detectable goitre only by palpation and invisible, even when thehead is stretched. More voluminous thyroid than usual, the lobeshave a volume that is at least equal to the volume of the lastphalanx of the subject’s thumb.

Ib Palpable and visible goitre when the head is stretched. Also all thecases where there is a nodule - even when there is no goitre.

II Visible goitre when the head is in a normal position.

III Very big goitre, visible from a distance

IODE DEFICIENCY SEVERE MODERATE MILD

Number of cases ofgoitre among theschool children (6-12)

visible goitretotal goitre

> 50 %> 10 %

20-49 %5-9 %

10-19 % 1-5 %

Urinary Iodine

Reflects directly intakeIs best to follow up programme response,

goitre takes time to decrease in sizeSamples needed are smallerTechnique is simple and not expensiveSamples can be taken easily, cheap,

acceptable and don’t need conservation techniques

Table 5. Epidemiological criteria for assessing iodine nutritionbased on median urinary iodine concentrations in school-aged childrenMedianurinaryiodine

Iodine intake(µg/L)

Iodine nutrition

< 20 Insufficient Severe iodine deficiency20-49 Insufficient Moderate iodine deficiency50-99 Insufficient Mild iodine deficiency100-199 Adequate Optimal200-299 More than adequate Risk of iodine-induced

hyperthyroidism within 5-10 yearsfollowing introductionof iodized salt in susceptible

> 300 Excessive Risk of adverse health consequences(iodine-induced hyperthyroidism,autoimmune thyroid diseases)

From WHO/UNICEF/ICCIDD (2)

Endemic cretinism

Neurological Severe motor and mental deficit cerebral palsy deafness, mutism euthyroid

Myoedematous Severe mental deficit Hypothyroid, destruction of the thyroid Iodine deficiency combined with goitrogens

and Se deficiency

Control strategies

Supplementation: injections, oralFortificationchanging food habits

Supplementation

Need to start early in pregnancysupplement women of child bearing ageOperational difficultiesInjections and hepatitis and HIVCovers need for about 4 years injectionsOral covers needs for one year

Fortification

Add iodine to a vehicle: salt or waterAdditive must be stable, not change the carrierNo by-pass, centralised productionNeed for a comprehensive approachPackaging, evaporationAccess of all the population to the fortified

foodPolicy and protection of the marketWho pays?Success story of Iran

Food habits

Very limited approach, food reflects iodine soil content

Control complications

Need for intensive follow upChanging consumption patterns in saltVariations in salt consumption Transient hyperthyroidism