A ppt on THYROID HORMONESAND THYROID INHIBITORS By Dr.Nanita Agrawal, Dr. Prashant,MD Pharmacology4students.com [email protected] 1dr prashant's

A ppt on

THYROID HORMONESAND THYROID INHIBITORS

By Dr.Nanita Agrawal, Dr. Prashant ,MD

[email protected]

1dr prashant's

www.pharmacology4students.com

THYROID HORMONESAND

THYROID INHIBITORS

dr prashant's www.pharmacology4students.com

I. THYROID HORMONEA. 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's www.pharmacology4students.com

B. ACTIONS• Growth and development: Essential for

normal growth and development.

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

• Calorigenesis: Increase BMR.

• CVS: Heart rate, contractility and output are increased.

• GIT: Propulsive activity increased.4dr prashant's


•Nervous system: Mental retardation is the hallmarkof cretinism.

•Skeletal muscle: Muscles flabby and weak in myxoedema.

•Kidney: Rate of urine flow is often increased.

•Haemopoiesis: Facilitatory to erythropoiesis.

•Reproduction: Indirect effect on reproduction.


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's


D. PREPRATIONS

• 1-thyroxin sod:

Electroxin

Roxin 100 ug tab.

Thyranorm

Thyrox 25 ug, 50 ug, 100 ug tabs. 7dr prashant's www.pharmacology4students.com

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:

• Thyroid nodule: 8dr prashant's


• 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 anaemiasMenstrual disorders, infertility not

corrected by usual treatment.Chronic/ non healing ulcersObstinate constipation


2. THYROID INHIBITORS

A. INTRODUCTION

Drugs used to lower the functional capacity of the hyperactive thyroid gland.

Throtoxicosis

Two main causes are Grave’s disease and toxic nodular goiter


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.

• Destroy thyroid tissue Radioactive iodine .11dr prashant's


3. ANTITHYROID DRUGS

A. INTRODUCTION

Inhibit iodination of tyrosine residues in thyroglobulin.

Inhibit coupling of iodotyrosine residues to form T3 and T4.


B. PHARMACOKINETICS

• Quickly absorbed orally

• Cross placenta

• Metabolised in liver

• Excreted in urine


C. ADVERSE EFFECTS

• Hypothyroidism due to over treatment common but reversible.

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

• Loss or graying of hair, loss of taste, fever and liver damage.

• Agranulocytosis 14dr prashant's www.pharmacology4students.com

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, maintenance dose 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's


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. 16dr prashant's www.pharmacology4students.com

F. ADVANTAGES OVER SURGERY

• No surgical risk

• Hypothyroidism, if induced, is reversible.

• Can be used even in children and young adults.


G. DISADVANTAGES

• Prolonged treatment is needed.

• Not practicable in uncooperative/ unintelligent patient.

• Drug toxicity.


4. IODINE AND IODIDES

A. INTRODUCTION

• Inhibition of hormone release- ‘thyroid constipation’.

B. PRERARATION AND DOSE

Lugol’s solution Colloid iodine 10% Collosol


C. USES

• Preoperative preparation

• Thyroid storm

• Prophylaxis of endemic goiter

• Expectorant

• Antiseptic 20dr prashant's www.pharmacology4students.com

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.


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.

131I emits x-rays as well as B particles.22dr prashant's


• 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.


• Diagnostic 25-100 u curie is given.

• Therapeutic

• Average therapeutic dose is 3-6 m curie.


B. ADVANTAGES

• Treatment is simple, conveniently inexpensive.

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

• Cure is permanent.


C. DISADVANTAGES

• Hypothyroidism

• Long latent period of response.

• Contraindicated during pregnancy- cretinism.

• Not suitable for Young patients.26dr prashant's


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


Our other websites

Naukridoctors.com

Anatomy4students.com

Biochemistry4students.com

Microbiology4students.com

Psm4students.com

Paediatrics4all.com

dr prashant's www.pharmcology4students.com

28

We thank our students who attend our classes in large

numbers and motivate/encourage us to learn and teach better.

You can also send any study material suitable for undergrads to us at

[email protected]

Documents

A ppt on THYROID HORMONESAND THYROID INHIBITORS By Dr.Nanita Agrawal, Dr. Prashant,MD Pharmacology4students.com [email protected] 1dr prashant's