Thyroid hormones are synthesized from tyrosine and iodine in the thyroid gland and regulate growth, metabolism, and other bodily functions. Anti-thyroid drugs work by inhibiting thyroid hormone synthesis, blocking iodine uptake, or destroying thyroid tissue. Synthesis inhibitors like propylthiouracil and methimazole bind to enzymes to prevent formation of the active hormones T3 and T4. Iodine and iodide supplements cause feedback inhibition of TSH to shrink the thyroid gland. Radioactive iodine I-131 is selectively taken up and destroys thyroid cells through radiation emission, providing a non-surgical treatment for hyperthyroidism.

1. THYROID &ANTI THYROID DRUGS

2. Thyroid hormone synthesis
• Tyrosine (an amino acid )two molecules get
condensed into Thyronine
• Iodide uptaken in thyroid tissues, get oxidized
with enzymes thyroid peroxidase releases iodine
which get combined with tyrosine to form
Monoiodotyrosine & diiodotyrosine (MIT & DIT)
• MIT &DIT get coupled with the help enzymes
peroxidase to form T3 & T4 (triiodothyronine&
Tetra iodothyronine)
• T3&T4 stored as thyroglobulin in lysosomes.

3. ACTIONS
• Growth & development - it's deficiency called
cretinism, causes delayed organogenesis &
tissue development, impaired intelligence &
mental functions including lethargic effects.
• BODY TEMPERATURE have positive
Calorogenic action due to increased bmr
• OTHER ORGANS & SYSTEMS Stimulate heart
,increased contractions, heart rate &output
manifest as fast bounding pulse

4. METABOLIC EFFECT
• Involved in lipid, carbohydrates & protein
metabolism
• Increases lipolysis & cholesterol metabolism.
Enhances more cholesterol conversation to bile
acids
• Glycogenolysis & gluconeogenesis increased, but
peripheral glucose utilization also increased. Net
effect is increased blood sugar levels .
• Proteolytic action stimulates , have catabolic
effect results negative nitrogen balance & tissue
wasting

5. • ACTION ON MUSCLE deficiency causes
flabby & weak muscles, also effect smooth
muscle deficiency causes constipation &
excess causes diarrhea
• CNS ACTIONS deficiency causes sluggish
mental functions deficiency causes tremors,
anxiety, nervousness
• ACTION ON erythropoiesis & reproductive
activities have positive effects

6. Uses
• Used as replacement therapy in cretinism and
myxedena.
• Levothyroxine(T4) given orally is the
preparation of choice

7. ANTI THYROID DRUGS
A. Synthesis inhibitors: e.g.propylthiouracil,
carbimazole, methimazole
B. Hormone release inhibitors: e.g. iodine,
iodide of sodium & potassium, organic iodide
C. Thyroid tissue destroyer : e.g. radioactive
iodine.

8. SYNTHESIS INHIBITORS
MOA
• drugs bind to enzymes peroxidase thereby
inhibit iodination of tyrosine hence MIT & DIT
not formed also inhibit coupling of MIT & DIT
to form T3 & T4
• Propylthiouracil in addition also prevent
conversion of tT4 into T4

9. SYNTHESIS INHIBITORS
• Pharmacokinetics(P/k)All are orally well
absorbed, wide distribution in body, milk,
placenta. Metabolized in liver, excreted in urine
• Adverse drug Reactions (ADRs) g i intolerance,
skin rash, joint pain. Overdose can cause
hypothyroidism, goitre. Rarely agranulocytosis
• USES used in hyperthyroidism, results seen in 1-2
wks

10. IODINE & IODIDE
• MOA- bcoz of excess of iodide in periphery
there is feed back inhibition of tsh leading to
thyroid tissue Shrinkage gland becomes firm &
less vascular. Peak effect seen in 10-15 days
• It is generally used before surgical thyroidectomy
which facilitates surgery there is less bleeding &
firm cut of tissue
• ADRS Mucous membrane inflammation, swelling
of eyes, lips, eyes, fever, angioedema, rarely
thrombocytopaenia

11. TISSUE DESTROYER
• radioactive iodine -I 131 is used, it's
preferencially taken up by thyroid gland, x rays
& β particles are emitted which destroy gland
cells in vicinity.
• It's action is monitored & only required amt
of tissues is destroyed. it's a type of medical
thyroidectomy