Iodine Flashcards
- _______ trace element discovered
- Deficiencies generally ________ patterned
- Deficiencies high in areas with low _____ levels of iodine
- Usual functions in ionic form I- (_____)
- Human body contains __-__ mg (75% in the thyroid)
Earliest
geographically
soil
Iodide
15-20
Iodine- absorption, metabolism, excretion:
- > __% rapidly absorbed in anion form (iodide) throughout the GI tract
- Free iodide appears in the ___
- Selectively trapped and concentrated in the _____ gland by Na+/I- symporter. - Operates using a __+/_+ ATPase pump
- Also found in _____, _____, ___, ______ & _______ _____
- Oxidised to ______ (I2) in thyroid
- Bound to tyrosine residues of thyroglobulin (a _______)
(form basis of T3 and T4) - Most excess excreted in _____
90
blood
thyroid
Na/K
ovaries, placenta, skin, salivary & mammary glands
iodine
glycoprotein
urine
Iodine- functions
- Synthesis of thyroid hormones (T3 & T4)- by the thyroid gland
- Thyroid hormones have a wide range of functions including regulation of:
- Growth and development of tissue (including CNS)
- Body temperature
- Metabolic rate
- Reproduction
- Nerve and muscle function
& more
Iodine deficiency- ______
- ________ of thyroid gland
- If inadequate Iodine intake, the
thyroid gland attempts to adapt
to the increased need to
produce hormones
→_______- of thyroid cells
- May be no physical symptoms
- Decreases ______, even after
iodine repletion
goitre
swelling
Hyperplasia
physical
slowly
Neo-natal hypothyroidism
Caused by iodine deficiency in _______ and early _____-
_____ period
decreased thyroid hormone
production in a newborn. In very rare cases, no hormone
is produced
pregnancy and early post-
natal period
Thyroid hormones, and therefore Iodine, are essential for
______ _________
brain development
Iodine deficiency is the World’s greatest single cause of _______ _____
______ and _______ disability (social consequences
and national development)
preventable brain damage
intellectual
consequences of deficiency can include
- Intellectual disability
- Impaired growth
- Heart problems
- May also be hearing and/or speech impairment
- Distinctive physical signs & symptoms
- Puffy-appearing face, Dull look, Thick, protruding
tongue, Lack of muscle tone, Abnormally large
fontanelles (soft spots of the skull), Broad hands with
short fingers, widely separate skull bones
______ _________ is the preferred terminology
due to negative connotations of “cretinism”
Congenital hypothyroidism
Iodine Deficiency Disorders (IDD):
- Major international public health problem. One of the three main
micronutrient deficiencies world-wide (iron, vitamin A, iodine) - Major cause- inadequate dietary intakes
- Many regions have soil with low iodine and/or consume low iodine
containing freshwater seafood - Exposure to anti-thyroid compounds (goitrogens) prevent uptake if iodine
by thyroid e.g. soy foods, ‘brassica’ vegetables- may be inactivated by
cooking. Also non-food goitrogens e.g. Br, Li
Iodine Deficiency - Australia:
* Around one in every ____ (__ per cent) women of childbearing age had an
iodine deficiency (defined as less ___ μg/L)
* Nearly ___ ____ (__ per cent) had an iodine level less than ____ μg/L
five
18
50
two thirds
62
150
Dietary sources of iodine
- Iodized salt (but, limit salt intake!)
- Foods of marine origin (e.g. fish, shellfish, kelp)
- Plants and animals (depending on soil content)
- Dairy products (iodine concentrated in mammary
glands, iodine-based sanitisers)
Iodine- toxicity:
* Intakes >_________μg/day
* Can produce similar symptoms of deficiency- hypertrophy, elevated ___
* Can increase risk of autoimmune ______ disease
* Acute I toxicity → burning of the mouth, throat, stomach, nausea, vomiting, diarrhoea, fever
2000μg
TSH
thyroid
Assessment of Iodine status
-Biochemistry
* Daily Iodine intake = urinary Iodine * 0.0235 * bw (kg)
* Urine excretion > 100 μg/L → adequate intake
< 100 μg/L → inadequate
< 50 μg/L → moderate deficiency
↓thyroid hormone secretion
< 20 μg/L → severe deficiency
* TSH concentrations > 5 μU/L suggest deficiency
* Thyroglobulin > 10 μg/L suggest deficiency
- Clinical
* Assessment of goitre
