thyroid 2 final

8/6/2019 Thyroid 2 Final

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A ppt on

THYROID HORMONESAND THYROIDINHIBITORS

By

Dr.Nanita Agrawal, Dr. Prashant ,MD

Pharmacology4students.com

[email protected]

1dr prashant'swww.pharmacology4students.com


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THYROID

HORMONESAND

THYROID INHIBITORS

dr prashant'swww.pharmacology4students.com


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I. THYROID HORMONE

A. INTRODUCTION

The thyroid hormone secretes 3 hormones:

1. Thyroxine (T4)2. Tryiodothyronine (T3)

3. Calcitonin

Former 2 are produced by thyroid follicles.

Calcitonin produced by interfollicular c cells.3dr prashant'swww.pharmacology4students.com


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B. ACTIONS

Growth and development: Essential for normalgrowth and development.

Intermediary metabolism: Marked effect on lipid,carbohydrate and proteinmetabolism.

Calorigenesis: Increase BMR.

CVS: Heart rate, contractility and output are

increased.

4dr prashant's

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acology4students.com


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Nervous system: Mental retardation is thehallmarkof cretinism.

Skeletal muscle: Muscles flabby and weak inmyxoedema.

Kidney: Rate of urine flow is often increased.

Haemopoiesis: Facilitatory to erythropoiesis.

Reproduction: Indirect effect on 5dr prashant'swww.pharmacology4students.com


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C. MECHANISM OF ACTIONS

T3 (and T4) penetrate cells.

Combine with a nuclear receptor.

A specific DNA sequece called thyroid hormone

response element has been identified.

T3-receptor complex binds.

Derepression of gene transcription 6dr prashant'swww.pharmacology4students.com


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D. PREPRATIONS

1-thyroxin sod:

Electroxin

Roxin 100 ug tab.

Thyranorm

Thyrox 25 ug, 50 ug, 100 ug tabs.7dr prashant's

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E. USES

Cretinism: Due to failure of thyroid development.Detected during infancy or childhood. Mental

retardation.

Adult hypothyroidism: Develops as a consequence

of thyroiditis, thyroidectomy, treatment with

goiterogens; may accompany simple goiter if iodine.

Myxoedema coma:

Th roid nodule:8dr prashant's



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Nontoxic goiter: May be endemic or

sporadic.deficient production of thyroid hormone

leads to excess TSH-throid enlarges.

Papillary carcinoma of thyroid:

Empirical uses:

Refractory anaemias

Menstrual disorders, infertility not corrected byusual treatment.

Chronic/ non healing ulcers

Obstinate constipation 9dr prashant'swww.pharmacology4students.com


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2. THYROID INHIBITORS

A. INTRODUCTION

Drugs used to lower the functional capacity of the

hyperactive thyroid gland.

Throtoxicosis

Two main causes are Graves disease and toxic

nodular goiter10dr prashant's



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B. CLASSIFICATION

Inhibit hormone synthesis (Antithyroid drugs)propylthiouracil, methimazole, carbimazole.

Inhibit iodide trapping (ionic inhibitors)thiocynates (-SCN) , perchlorates (-C1O4), nitrates

(-NO3).

Inhibit hormone release iodine, iodides of Na and

K, organic iodide.

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3. ANTITHYROID DRUGS

A. INTRODUCTION

Inhibit iodination of tyrosine residues inthyroglobulin.

Inhibit coupling of iodotyrosine residues to formT3 and T4.



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B. PHARMACOKINETICS

Quickly absorbed orally

Cross placenta

Metabolised in liver

Excreted in urine



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C. ADVERSE EFFECTS

Hypothyroidism due to over treatment common butreversible.

G.I. Intolerance, skin rashes and joint pain.

Loss or graying of hair, loss of taste, fever and liver

damage.

Agranulocytosis14dr prashant'swww.pharmacology4students.com


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D. PREPARATIONS AND DOSE

Propyltjiouracil : 50-150 mg TDS followed by 25-

50 mg BD-TDS for maintenance PTU 50 mg tab.

Methimazole: 5-10 mg TDS initially, maintenance

dose 5-15 mg daily in 1-2 divided doses.

Carbimazole: 5-15 mg TDS initially, maintenancedose 2.5-10 mg daily in 1-2 divided doses, neo

mercazole, thyrozole, antithyrox 5 mg tab.

Carbimazole is more commonly used in india. 15dr prashant'swww.pharmacology4students.com


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E. USES

The following strategies are adopted:

1) Definitive therapy: Preferred in young patient

with a short history.

2) Preoperatively: Carbimazole before performing

partial thyroidectomy.

3) Along with 131 I.



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F. ADVANTAGES OVER SURGERY

No surgical risk

Hypothyroidism, if induced, is reversible.

Can be used even in children and young adults.



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G. DISADVANTAGES

Prolonged treatment is needed.

Not practicable in uncooperative/ unintelligentpatient.

Drug toxicity.



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4. IODINE AND IODIDES

A. INTRODUCTION

Inhibition of hormone release- thyroid

constipation.

B. PRERARATION AND DOSE

Lugols solution

Colloid iodine 10%19dr prashant'swww.pharmacology4students.com


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C. USES

Preoperative preparation

Thyroid storm

Prophylaxis of endemic goiter

Expectorant

Antiseptic 20dr prashant'swww.pharmacology4students.com


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D. ADVERSE EFFECTS

Acute reactions: Swelling of lips. Eyelids,

angioedema of larynx (may be dangerous), fever,

joint pain.

Chronic overdose (iodism): Long term use of high

doses can cause hypothyroidism and goiter.



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5.RADIOACTIVE IODINE

A. INTRODUCTION

131I: Physical half life 8 days- most commonly

used.

123I: Physical half life 13 hours- only rarely used

diagnostically.

125I: Physical half life 60 days.

-22dr prashant'swww.pharmacology4students.com


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B particles utilized for their destructive effect on

thyroid cells.

131I is concentrated by thyroid.

Incorporated in colloid- emits radiation from within

the follicles

Thyroid follicular cellsundergo pyknosisand

necrosis followed by fibrosis.



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Diagnostic 25-100 u curie is given.

Therapeutic

Average therapeutic dose is 3-6 m curie.



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B. ADVANTAGES

Treatment is simple, conveniently inexpensive.

No surgical risk, scar or injury to parathyroids/recurrent laryngeal nerves.

Cure is permanent.

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C. DISADVANTAGES

Hypothyroidism

Long latent period of response.

Contraindicated during pregnancy- cretinism.

Not suitable for Young patients.

26dr prashant's



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6. B ADRENERGIC BLOCKERS

Propranolol

During thyrotoxic crisis.

While awaiting response to carbimazole or 131I.

Along with iodide for preoperative preparation

before subtotal thyroidectomy.27dr prashant's



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