Iodine and its compounds play an important role in thyroid hormone production and metabolism. Iodine deficiency can cause hypothyroidism while excess can lead to hyperthyroidism. Sodium iodide is commonly used for iodine supplementation and treatment of thyroid conditions. Radioactive iodine isotopes like 131I are used in diagnosis and treatment of thyroid disorders.

1. Prepared By
Mr. Subodh V. Kamble
M. Pharm (Pharmaceutical Chemistry)
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2. 1. Introduction
2. Importance of Iodine
3. Hypo & Hyperthyroidism
4. Compounds Containing Iodine
5. Radioactive Iodine & Sodium Iodide
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3.  Iodine (as iodide) is one of the essential trace
element.
 Iodine, its compounds and preparations have
to be considered from the following points
a) Its systemic use and biochemical role
b) Iodine and its preparations for topical applications
 This chapter mainly deals with the iodine &
its compounds from the point of its systemic
use and biochemical role.
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4.  The usual daily requirement of iodine in an
average
Male 140 micrograms (mcg)
Female 100 micrograms (mcg)
 The daily requirement is usually obtained
from diet.
 Sources:
◦ Common table salt, eggs, cod fish, yogurt.
◦ Now-a-days sufficient intake of iodine can be
achieved by using iodized table salt (0.01% NaI).
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5.  Iodide ingested along with food after absorption
reaches blood circulation and plays an important
role in the synthesis of two important thyroid
hormones known as Thyroxine and
Triiodothyronine.
 These hormones are essential for the normal
growth & development and plays imp. role in
energy metabolism.
Thyroxine Triiodothyronine 5

6.  Thyroxine is a storage form of Hormone and
Triiodothyronine is a circulating form.
 The important function of thyroid hormones
is to increase the metabolic rate through
increasing the oxidative processes in the
body.
 Iodine can be administered internally which
is reduced to iodide in GIT.
 Because of insolubility of iodine, the salts of
iodine like sodium iodide is preferred for
internal administration.
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7.  The iodide is normally utilised for the synthesis of
thyroid hormones.
 After the administration of iodine (iodide) its
uptake is governed by various factors like:
1. Condition of local thyroid tissue.
If it is tumorous then uptake is slower than normal tissue.
2. The conc. of inorganic iodide in the blood
High levels keep the iodine in high levels in colloids and
thus only small part of administered iodide is utilized.
3. An anterior pituitary hormone thyrotropin levels in blood.
directly related in utilization of iodine in the formation of
thyroid hormones and it also controls the release of
thyroid hormones from thyroid glands.
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8.  Deficiency of thyroid hormone cause
Hypothyroidism.
 A disease condition in which all metabolic
processes are slowed down and leads to
goiter (enlargement of thyroid gland)
characterized by swelling of neck.
 Cretinism (Mental retardation, dwarfism) is a
clinical condition of deficiency of thyroid
hormone since birth.
 For treatment suitable iodine compounds like
Sodium Iodide or Potassium Iodide are used.
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9.  The excessive secretion of thyroid hormone
causes Hyperthyroidism.
 The severe form of this is detected by
Exopthalamous (enlargement of Eye balls).
 For treatment antithyroid drugs like
carbimazole and methimazole are used.
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10. I2 Mol. Wt. 253.8
 It contains 99.5 – 100.5 % w/w of I2
 Physical Properties:
◦ It occurs as a heavy, bluish –black rhombic prism or
plate with metallic luster.
◦ It has peculiar odour and volatilises at ordinary
temp. and at high temp. it melts.
◦ It is practically insoluble in water but soluble in
alcohol.
◦ It is freely soluble in chloroform and solvent ether.
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11.  Chemical Properties:
1. It combines directly with some non-metals and
with metals
Fe + I2 FeI2
2. Reducing agents react with aq. Iodine solution &
get oxidized.
2Na2S2O3 + I2 2NaI + Na2S4O6
(Sodium Tetrathionate)
3. Iodine reacts with alkali to form an iodide and
iodate when heated.
3I2 + 6NaOH 5NaI + NaIO3 + 3H2O
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12.  Assay:
◦ It is assayed by oxidation reduction titration method.
 Uses:
◦ It is used in the form of its aqueous and alcoholic
solutions as germicide and fungicide.
◦ It is used in the treatment of thyrotoxicosis
(hyperthyroidism).
◦ For purification of drinking water.
◦ As an antidote in alkaloidal poisoning.
◦ In Thin layer chromatography it is used as locating
agent.
◦ It is also used in oxidation-reduction titrations as
oxidizing agent.
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13.  Incompatibilities:
◦ The reaction of iodine with turpentine is violent.
◦ It reacts with ammonia or ammoniated mercury to
form explosive iodide of Nitrogen.
◦ It reacts with alkali hydroxides and carbonates to
form iodide or iodates.
◦ If the aq. Solutions of alkaloidal salts are treated
with iodine, alkaloids are precipitated.
 Storage:
◦ It is stored in amber colored bottles with tight glass
stopper and kept in cool place.
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14. NaI Mol. Wt. 149.9
Sodium iodide is official in B. P., It contains 99 –
100.5% of NaI.
 Preparation:
◦ It is prepared by adding slight excess iodine to the conc.
NaOH, which gives a mixture of Sod. Iodide and Sod.
Iodate.
◦ The reaction mix is evaporated to dryness and the residue
is treated (reduced) with carbon to convert Sod. Iodate to
Sod. Iodide.
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15.  Properties:
◦ It is a white crystalline odourless powder.
◦ It is hygroscopic (taking water from moisture) in
nature and stable in dry air.
◦ It may decompose on storage and develops brown
color (air, oxidation causes liberation of free
iodine).
◦ Sodium iodide is soluble in water and alcohol.
◦ The aq. Solution gives yellow precipitate with silver
nitrate.
NaI + AgNO3 AgI + NaNO3
◦ Oxidizing agents liberate iodine in acidified
solutions.
2NaI + H2SO4 + H2O I2 + 2H2O + Na2SO4
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16.  Assay:
◦ It is assayed by oxidation-reduction type of
titration.
 Incompatibilities:
◦ It get decomposed in presence of acid with
liberation of iodine.
◦ Iodides precipitates aq. Solution of alkaloids.
 Storage:
◦ Stored in well closed container and kept in a dry
place.
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17.  The iodide acts as fibrolytic agent in Syphilis
and Leprosy.
 They are also used in fungal infections.
 Potassium iodide is used as expectorant.
 It is also useful in treatment of Asthma and
chronic bronchitis.
If iodides are used in excessive doses, the toxic
symptoms observed as irritation of skin & mucous
membrane and known as Iodism.
Characterized by rashes, headache etc.
Sodium chloride is administered for rapid removal
of iodide.
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18.  Isotopes: Elements having the same atomic
no. but differ in atomic weight or mass are
known as Isotopes.
e. g. ,
◦ There are two major types of isotopes:
1. Stable Isotopes or nuclide
2. Unstable Isotopes or radioactive isotopes or
radionuclide.
 There are several radioactive isotopes of
Iodine.
 131I is obtained by irradiation of tellarium and
used in the form of sodium iodide (131I ).
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19.  The solution of sodium iodide (131I ) is official in
B. P. 1988.
 The activity should be 90 – 110 %
 Properties:
◦ It is a clear colorless solution.
◦ It has a half life of 8.04 days and emits beta & gamma
radiations.
◦ The solution has pH between 7 -10.
 Uses:
◦ It is most widely used for the diagnosis of disorders of
thyroid function (hypothyroidism, hyperthyroidism and
goiter) and for the treatment of hyperthyroidism.
 123Iodine has a half life of 13 days and emits X-rays, so
used for thyroid scan.
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