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Iodine
Iodine is an essential micromineral, is important as
an integral component of thyroid hormones, and
is required for normal growth and metabolism.
The adult body contains approximately 15 – 20mg of iodine, 70 – 80%
of which is found in the thyroid gland. Requirements for iodine may
increase with altered thyroid function, and in particular during pregnancy
and lactation. Iodine is especially important for the development of the
brain and nervous system of the child. The Australian Recommended
Dietary Intake of iodine is 225μg for pregnancy and 270μg for lactation.
Indications:
May help support healthy thyroid function
May help support
increased iodine requirements during pregnancy
Pack Size: 60 capsules
May help support normal brain development and cognition
Recommended Dose:
1 capsule per day or as
recommended by your
healthcare professional
Each capsule contains:
Iodine (as potassium iodide)
225 µg
Excipients:
Toxicity:
Silica, glycine, leucine, vegetable capsule
Iodine toxicity is rare, however, chronic overconsumption
reduces organic binding of iodine by the thyroid
gland, leading to hypothyroidism and goiter.3
Interactions:
Goitrogens may affect the uptake of iodine, organification
of iodine, or hormone release from thyroid cells.1
Contraindications/Precautions:
Increased intake of iodine in persons with hyperthyroidism
promotes further hormone production. Chronic intake of
several milligrams per day may disrupt thyroid function.2
The safe upper limit of iodine is 1,000µg (1mg). Where
supplementation exceeds 20mg of iodide it may
potentially contribute to thyroid pathology in those
with Hashimoto’s thyroiditis and Graves’ disease,
or worsen nodularities in euthyroid individuals.4
This information is for healthcare professionals only
Call 1800 625 934 / visit www.dvpi.com.au
Technical Information
Healthy thyroid function
Iodine is an essential micronutrient and component of
thyroid hormone synthesis and function.7 It typically
functions in its ionic form iodide. Dietary iodide is
completely and rapidly absorbed and distributed
throughout the extracellular fluid from where it permeates
all tissues. However, the thyroid gland traps iodide most
aggressively by way of a sodium-dependant active
transport system and against an iodide gradient.1
As illustrated in figure 1, iodide is converted to iodine and
then condensed onto tyrosine residues on the backbone of
a thyroglobulin molecule. The resulting iodothyroglobulins
(mono-iodinated tyrosine or MIT and di-iodinated tyrosine
or DIT) form the most important constituents of the colloid
material present in the thyroid unit. Two DIT molecules
coupled together form thyroxin (T4), while a DIT and a
MIT result in the formation of tri-iodothyronine (T3). The
majority of T3, which is known to be more biologically
active than T4, is produced by peripheral conversion from
T4 in a deiodination reaction. Both T3 and T4 are released
from the thyroid gland into the blood stream by proteolysis
and then bound to thyroid hormone binding protein,
predominantly thyroxin binding globulin (TBG), which
accounts for about three quarters of the bound hormone.9
Synthesis of Thyroid Hormones
Via a negative feedback mechanism, the hypothalamus
secretes thyrotropin-releasing hormone (TRH), which
stimulates the pituitary to produce thyroid-stimulating
hormone (TSH), which in turn signals the thyroid gland
to capture iodine from the blood in order to synthesize,
store, and release T4. T4 is converted to its biologically
active form T3 once it reaches its target cells.10
Increased iodine requirements during pregnancy
Thyroid dysfunction is extremely common in women,
affecting menstrual cyclicity and reproduction.
Even mild forms of hypothyroidism increase the
rate of miscarriage, foetal death, or adverse
effects on later cognitive development.11
During pregnancy adequate quantities of iodine are
required to prevent neonatal and maternal hypothyroidism,
and trophoblastic and embryonic/foetal disorders
that lead to permanent sequelae in infants.5
The World Health Organisation (WHO) recommends
an intake of at least 200µg of iodine per day during
pregnancy and postpartum5, a dosage that is considered
effective without producing side effects or enhancing the
frequency of postpartum thyroiditis.12 A recent extensive
and critical review of the literature established a
recommendation of 150-230µg/day of iodine during
pregnancy, lactation and the neonatal period.13
Normal brain development and cognition
Maternal hypothyroxaemia in early pregnancy, of
which iodine deficiency is the most common cause,
is potentially damaging for foetal brain development.
Even mild to moderate hypothyroxinaemia may result in
suboptimal neurodevelopment as the cerebral cortex of
the foetus depends on maternal T4 for the production
of T3.14 A preliminary meta-analysis of 36 studies on
the impairment of intelligence development caused
by iodine deficiency showed that iodine deficiency
leads to a loss of 10 points of IQ, while 11.5 points
can be gained following iodine supplementation.15
Hormone output via the thyroid is regulated with the
aid of both the hypothalamus and the pituitary gland.
References available on request
This information is for healthcare professionals only
Call 1800 625 934 / visit www.dvpi.com.au
1500610
Figure 1: Iodine’s role in thyroid hormone function
Randomized controlled trials have shown that iodine
supplementation in moderately iodine-deficient school
children improved information processing, fine motor
skills, and visual problem solving. Improvement in iodine
status, rather than iodine status itself, was shown to
determine mental performance in these children.16, 17