The document summarizes thyroid hormones and anti-thyroid drugs. It discusses the thyroid gland's structure and location in the neck. The thyroid secretes T4, T3, and calcitonin hormones which regulate growth, metabolism, and other bodily functions. The synthesis of T4 and T3 involves iodide uptake, oxidation, iodination, and coupling steps. Anti-thyroid drugs like propylthiouracil and carbimazole inhibit hormone synthesis. Radioactive iodine isotopes can destroy thyroid tissue to treat hyperthyroidism while drugs like propylthiouracil and carbimazole are used to inhibit hormone synthesis.

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THYROID
HORMONES
&
ANTI THYROID
DRUGS
By
Mr.S.KAMESHWARAN.,M.Pharm.,(Ph.D).
Associate Professor, Excel College of Pharmacy
Komarapalayam, Namakkal, Tamilnadu, India.

2. THYROID GLAND
The thyroid gland is a butterfly-shaped
organ,
It is composed of two cone-like lobes or
wings, lobus dexter (right lobe) and lobus
sinister (left lobe), connected via the
isthmus,
The organ is situated on the anterior side of
the neck.

4. 4
●Regulation of thyroid function
TRH: thyrotropin-releasing hormone
TSH: thyroid-stimulating hormone

5. Thyroid gland secretes 3 hormones:
THYROXINE (T4),
TRI IODOTHYRONINE (T3),
CALCITONINE.
T4, T3 is produced by Thyroid follicles.
Calcitonine is produced by intracellular – c cells.
Up to 80% of the T4 is converted to T3 by organs such as
the liver, kidney and spleen.
 T3 is several times more powerful than T4.

6. CHEMISTRY:
Both are iodine containing derivatives of
thyronine.
SYNTHESIS:
Synthesized and stored in thyroid follicles,
There are four major steps involved in the
synthesis of thyroid hormones,
♣ IODIDE UPTAKE,
♣ OXIDATION,
♣ IODINATION,
♣ COUPLING.

7. IODIDE UPTAKE:
Iodide trapping - stimulated by TSH,
(iodide trapping –Absorption of Iodide from
the bloodstream)
Thyroid cells have an active transport
process.

8. OXIDATION & IODINATION:
TRAPPED IODIDE CARRIED ACROSS THE APICAL
MEMBRANE BY A TRANSPORTER CALLED
“PENDRIN”
↓
THAT IODIDE IS OXIDISED BY MEMBRANE BOUND
THYROID PEROXIDASE ENZYME TO IODINIUM (I+)
IONS.
↓
IODINIUM (I+) IONS COMBINES WITH TYROSIL
RESIDUES OF THYROGLOBULIN
↓produce
MONOIODOTYROSINE & DI IODOTYROSINE

9. COUPLING:
Pairs of IODINATED TYROSIL residues coupled
together to form T3 & T4.
Stored in interior follicles as THYROID COLLOID.
Thyroid hormone secreted from the gland is
about 80-90% T4 and about 10-20% T3

11. ACTIONS:
GROWTH & DEVELOPMENT:
T3 & T4→ essential for normal growth and development,
Cells of the developing brain are a major target for the
thyroid hormones T3 and T4.
 Thyroid hormones play a particularly crucial role in brain
maturation during fetal development.
Decreased T4-T3 Secretion → CRETINISM (Arrest of
physical and mental development),
Acute hypothyroidism→ MYXOEDEMA (Slowing of
activity and weight gain).

12. CRETINISM
MYXOEDEMA

13. INTERMEDIATORY METABOLISM:
Thyroid hormone has marked effect on LIPID, CH &
PROTEIN metabolism.
CALORIGENESIS:
T4- T3→ increases BASAL METABOLIC RATE (BMR)
by stimulation of cellular metabolism,
They maintain body temperature.
CVS:
T3, T4 – Cause hyper dynamic state of circulation,
heart rate, contractility, increase in cardiac
output.

14. NERVOUS SYSTEM:
T3, T4 stimulates Mental retardation.
GIT:
Hypothyroidism- Constipation,
Hyperthyroidism- Diarrhoea.
REPRODUCTION:
Hypothyroidism may leads to impaired fertility.
CALCITONIN
It contributes to the regulation of blood calcium
levels,
Stimulates movement of calcium into bone.

15. THYROID DISORDERS
It includes
 Hyperthyroidism (abnormally increased activity),
 Hypothyroidism (abnormally decreased activity) and
 Thyroid Nodules, which are generally benign thyroid neoplasm,
but may be thyroid cancers.
 All these disorders may give rise to goiter, that is, an enlarged
thyroid.
PREPARATIONS:
• THYROXINE:
It should be administered in empty stomach to avoid food
interaction.
USED IN:
 Cretinism,
 Anti hypothyroidism,
 Myxoedema coma,
 Nontoxic goiter.

16. THYROID DRUGS
THYROXINE
LEVO THYROXINE
LIOTHYRONINE
LIOTRIX

Pharmacokinetics
easily absorbed; the bioavailablity of T4 is 80%, and T3 is
95%.
Drugs that induce hepatic microsomal enzymes (e.g.,
rifampin, phenbarbital, phenytoin, and etc) improve their
metabolism.

17. ADR:
Overmuch leads to thyrotoxicosis
Angina or myocardial infarction usually appears in ageds
Clinical use
1.Hypothyroidism: cretinism & myxedema
2.simple goiter:
3. Others:

18. GOITER

19. THYROID INHIBITORS / ANTI THYROID DRUGS
“Drugs used to lower the functional capacity of
hyper active thyroid gland”
 also called as thionamides
 Antithyroid drugs decrease the levels of the
two hormones produced by the thyroid,
[thyroxine (T4) and triiodothyronine (T3)]
THYROTOXICOSIS:
Excessive secretion of thyroid hormones induces 2 main
causes:
☻Graves disease (Autoimmune Disorder),
☻Toxic nodular goiter

20. Graves disease

21. CLASSIFICATION:
INHIBIT HORMONE SYNTHESIS
PROPYL THIOURACIL
METHIMAZOLE
CARBIMAZOLE
IODIDE TRAPPING INHIBITORS
THIOCYANATES
NITRATES
INHIBIT HORMONE RELEASE
IODINE
IODIDES OF SODIUM & POTASSIUM
ORGANIC IODIDE
DESTROY THYROID TISSUE
RADIO ACTIVE IODINE (I131, I125, I123)

22. INHIBIT THE HORMONE SYNTHESIS
DRUG + THYROID PEROXIDASE
↓
INHIBIT OXIDATION OF IODIDE
↓
INHIBIT IODINATION OF TYROSINE
↓
INHIBIT COUPLING OF IODOTYROSINE RESIDUES.
• Propylthiouracil inhibit peripheral conversion of T4 to T3,
• Carbimazole is 5 times more potent than propylthiouracil.

23. ADR:
• Hypothyroidism,
• Goiter.
USE:
• Along with I131
• Pre operatively.

24. IODIDE TRAPPING INHIBITORS
 Also known as ionic inhibitors
 Inhibit iodide trapping,
 At high concentration also inhibits iodination,
 Due to toxicities in liver, kidney, brain it is not widely used now.
IODINE AND IODIDES- INHIBIT HORMONE RELEASE
 Even though it is a constituent of thyroid hormone, it is the
fastest acting thyroid inhibitor.
 Directly act on thyroid cell, mechanism is not clear,
 But it produces thyroid constipation.

25. ADR:
♥ Swelling of lips, eye lids, and fever,
♥ Over dose-Iodism,
♥ Hypothyroidism and constipation.
USE:
♥ Pre operative preparation,
♥ Prophylaxis,
♥ Antiseptic.

26. DESTROY THYROID TISSUE
 They are the Stable isotopes of iodine is 127I.
 The following are the medically important radio isotopes:
 131I - t1/2 - 8 days
 123I - t1/2 - 13 days
 125I - t1/2 - 60 days
131I –emits X rays, β particles
 X rays – Used in TRACER study monitored by a counter,
 β particles – Destruction of thyroid cells,
 They Penetrate only 0.5- 2mm of tissues.

27. Advantages:
Simple, convenient ,inexpensive,
No surgical risk,
Permanent cure,
Disadvantages:
 Hypothyroidism,
 Contraindicated during pregnancy,
 Not suitable for young patients.

28. THANK U