Thyroid Flashcards
Hyperthyroidism pharmacology?
- Anti-thyroid medication
- Iodine
- Radioactive idoine therapy
- Surgery
- Adjunct therapy: Propranolol , Ca2+ channel blockers and Glucocorticoids
- Thyroid Storm
Hypothyroidism pharmacology?
- Levothyroxine sodium(T4)
- Liothyroxine(T3)
Anti-thyroid medication ?
Carbimazole converted to an active metabolite methimazole
Carbimazole MOA?
- Decrease uptake & concentration of the inorganic iodine by the thyroid
- Decrease formation of di-iodotyrpsine & thyroxine
3.
Carbimazole conversion and effects on throid Hs
Once converted to Methimazole prevents thr thyroid peroxidase enzyme from coupling & iodinating the tyrosine residues on the thyroglobulin therefore decreasing the production of thyroid hormones(T2/4)J
Where is carbimazole not used and why?
Not used in inflammatory thyroid disease since the release of performed thyroid hormone is not inhibited
What is biosynthesis of T3 & T4
Dietary iodine(I) ingestion (Absorbed into bloods stream as iodide)
↓
Uptake of iodide(I-) by thyroid gland
↓
Synthesis of thyroglobulin(precursor of thyroid hormone
↓
Idodide(I-) oxidized into Iodine(I) by thyroid peroxidase (METHIMAZOLE)
↓
Iodination of thryoglobin tyrosine residues=Monoiodotyrosine(MIT) + Diiosotyrosine(DIT)
↓
Coupling of iodotyrosine residues(MIT & DIT) → T3/4
Carbimazole caution?
Pregnancy
-Relatively safe at doses < 20mg/day
-No breastfeeding
-Do not combine with thyroxine
Carbimazole DI?
Warfarin , Heparin
-Enhances anti-coagulant effect
-Adjust dosage to prothrombin time
Carbimazole A/E?
Uncommon(1)
&
Uncommon(4)
Common:
-Itching
-Skin rash
Uncommon:
-Agranulocytosis(Sore throat & fever)
-Cholestatic hepatitis
-Mild arthralgia
-Alopecia
Iodine drug?
Lugol’s solutions(Potassium Iodide)
Iodine/Lugol’s solutions(Potassium Iodide) MOA?
- ↓ Thyroglobulin proteolysis(Proteolytic processing) ∴ ↓ thyroid hormone secretion(T3/4)
- Temporary inhibition of iodine organification in the thyroid gland(Wolf-Chaikoff effect)
Wolf-Chaikoff effect?
Temporary inhibition of iodine organification in the thyroid gland
Wolf-Chaikoff effect after two-four weeks?
However, within two or four weeks of continual exposure to excess iodine organification and thyroid hormone biosynthesus resumes normally-Escape from the Wolff-Chaikoff effect)
Iodine effects of thyroid hormone?
↑ Iodine concentration inhibits thyroid hormone synthesis and release
Iodine caution(2)?
- Renal Impairement→Hyperkalemia
- Pregnancy→ Neonatal goiter
→Neonatal hypothyroidism
(No breastfeeding)
Iodine DI?
-ACE-Inhibitors
-K+-sparring diuretics
All cause K+ overload
Iodine A/E?
Common(2)
Less Common(4)
Prolonged use(4)
Common:
1. Gastric irritation ∴ taken with meals
2. Bloody diarrhoea
Less Common:
1. Arthralgia
2. Fever
3. Lymphadenopathy
4. Hypersensitivity
Prolonged use:
1. Metallic use
2. Conjunctivitis
3. Painful salivary glands
4. ↑ salivation
Iodine Indications?
- Preoperative preparation for thyroidectomy in Graves disease
-Renders thyroid less vascular - Thyroid Storm
-Iodine blocks T4/T3 release within hours - Adjunctive therapy to antithyroid agents in Graves disease
- Protective after radioioiodine therapy
-Potassium iodidie blocks uptake of radioactive iodine isotopes by the thyroid glands thereby minimizing the risk of radiation-induced thyroid neoplasms
Radioactive idoine therapy name?
Sodium iodide 131I -capsule
Radioactive idoine therapy MOA?
Radioiodine-131 beta particles react with intracellular water in the thyroid gland to produce free radicals
-Destruction of the thyroid gland
Radioactive iodine therapy Dosage?
First dose:
Symptoms improve after 2 weeks
Second dose:
Given 6-12 weeks later to prevent recurrence
Radioactive iodine therapy CI?
- Pregnancy ∴ contraceptive advised for both treated men and women
- Paediatrics(not recommended)
- ↑Incidence of radiation-induced hypothyroidism
- Large toxic nodules goitres may require repeated doses
Radioactive iodine therapy disadvantage/
↑Incidence of radiation-induced hypothyroidism
Radioactive iodine therapy A/E?
- Painful radiation thyroiditis
- Radiation-induced thyroiditis
- Severe swelling
Radioactive iodine therapy indications?
- Hyperthyroidism
- Pre-operatively to reduce the vascularity of the gland
- Post operatively in the case of carcinomas to reduce recurrence
Surgery
Total or partial removal of the thyroid gland
&
Removal of bones of the orbit for decompression in the thyroid optic neuropathy
Adjunct therapy?
- Propranolol
- Ca2+ channel blockers
- Glucocorticoids
Propranolol
Indications:
Relieves tachycardia, tremors, palpitations, anxiety , state and tension
CI:
Cardiac Failure
Ca2+ channel blockers effects(2)?
-Control tachycardia
-↓Supraventricular tachyarrthymias
Glucocorticoids drug?
Prednisone
Thyroid storm?
Life-threatening exaggerated manifestations of hyperthyroidism
- Hyperthermia
*Severe cardiac failure
*Possible cardiac failure
*Severe agitation/mental disorientation
*Stupor & coma
Glucocorticoids effects?
Control inflammation
*Thyroid optic neuropathy (pressure on optic nerve)
→ Loss of eyesights
Thyroid storm intensive care?
- Carbimazole every 4-6hrs
- Iodine 8hrly
- Glucocorticosteridos hourly
- Propranolol hourly/Ca2+ - channel blockers
Hypothyroidism drugs?
- Levothyroxine sodium(T4)
- Liothyroxine(T3)
Levothyroxine sodium(T4)?
Synthetic thyroxine sodium
Levothyroxine sodium(T4) caution?
- CVS disorders → Severe ischemic heart disease
→Myocardial disease - Geriatics→ Dosage with ↓ with age
- Paediatrics→ used with caution
- Pregnancy → Limited crossing of placenta (No known A/E)
Levothyroxine sodium(T4) A/E?
- Dose related
Symptoms of hyperthyroidism
Levothyroxine sodium(T4) DI?
- *Calcium carbonate
*Ferrous sulphate
All ↓ absorption of levothyroxine
- Cholestyramine → Binds thyroxine in GIT, prevents absorption
- Warfarin → ↑ Warfarin effects
- Oestrogen→↑serum thryoid binding globin and alter thryoxine requirements
- Sympathomimetics→Mutual increase in effects/CVS
- Oral antidiabetic agents and insulin→ Requirements may change if thryoxine initiated for withdrawn
Levothyroxine sodium(T4) indications?
Pregnancy & congenital hypothyroidism -drug of choice
Hypothyroidism pharmacology drugs?
- Levothyroxine sodium T3
- Liothryoxine(T3)
Liothryoxine(T3)
- Response
- Strength
- Cautions
- Response very rapid thus given in acute situations only
- Strength
5x stronger than levothryoxine - Cautions in geriatics & paediatrics -tailor dose to individual requiremenys
Liothryoxine(T3) I?
- Cases where rapid response is required (Emergencies)
- Hypothyroid coma
- Sever hypothyroid state
- 5’-deiodinase deficient patients
Thyroid cancer
-Surgical Removal of carcinogenic nodules
-Benign nodules are harmless
Goitrous thyroid disease
-Lack of dietary iodine-thyroid gland enlarges in an attempt to produce more hormone
-Iodine supplementtaion
-If goite is too large:
-Breathing/swallowing difficulty
-If no response to treatment-surgery