Thyroid Gland Flashcards
Thyroid hormone preparation
Levothyroxine
Antithyroid agents
Thiomazole (methimazole), propylthiouracil
Iodide is oxidised to iodine by enzyme
Thyroid peroxidase
Iodine is added into
Tyrosine residue called thyroglobulin
Thyroid peroxidase also does
Conjugation of monoiodothyroxine and DIT to form T3 ;2 DIT conjunction to form thyroxine(T4)
T3 and T4 are released when
Thyroglobulin is proteolysed
10 %of T3 is formed from thyroid gland remaining 90from
T4from deiodisation done by iodothyronine deiodinase
Is T3or T4more active
T3 is 10x more active than T4
Fns of thyroid gland
Responsible for basic energy metabolism, Growth of body and development, Metabolism(increase gluconeogenesis and decrease glycogen synthesis, Nervous system dev and fn, stimulate beta adrenoreceptor expression in myocardium and increase catecholamine sensitivity in myocardium -increase O2 consul
Hypothyroidism
Decrease in thyroid hormones and their fn
In women hypothyroidism is usually
Subclinical and hormone replacement therapy is used
Hypothyroidism causes
Hyperthyroidism treatment, autoimmune thyroiditis, thyroid gland surgery, medication like amiodarone and lithium
Hyperthyroidism causes
Graves disease(Bazedovs), nodular toxic goiter
Treatment of hyperthyroidism
Radioactive iodine therapy or thyrostatic drug therapy (prevent iodine binding to thyroglobulin
Thyroxine synthesis occurs only in
Low iodine concentration, otherwise it inhibits
Thyrotropin releasing Hormone(TRH) and Thyroid stimuting hormone (TSH )other names
TRH:Thyroliberin,TSH: Thyrotropin
Carbimazole is a
Thiomazole prodrug
For symptomatic treatment of hyperthyroidism,use
Beta adrenoreceptor blocker
Levothyroxine (synthetic form of T4) action
On conversion to T3, stimulate intracellular thyroid receptors all over body-nuclear DNA ,gene expression and protein synthesis follows
Use of levothyroxine
Hypothyroidism, autoimmune hashimoto’s thyroiditis, replacement therapy after thyroidectomy
SE of levothyroxine
Tachycardia
Interactions of levothyroxine with
drugs like amiodarone and diet
Timing for levothyroxine
60 min before first meal and no other medications within 2 to 4 hours after administration
Levothyroxine reduce the effect of
Hypoglycemic agents
Mild intoxication of thyroid hormone caue
Sinus tachycardia, tremor, anxiety feeling of heat, agitation, sleep disorders
Severe toxicity of thyroid hormone cause
Supraventricular tachycardia, hyperthermia, hypertension and finally seizures and coma
Symptoms of acute levothyroxine overdose comes Only after
Approx 7 days delay due to T4 to T3 conversion time
Do we use antithyroid hormones in thyroid overdose?
No, only symptomatic treatment and on case of severe adreno stimulation use BAB
Thiomazole ((methimazole) action
Inhibit thyroid peroxidase and it’s fns
Thiomazole is
Embryotoxic, because it crosses placenta ( category D)
Propylthiouracil action
Inhibit thyroid peroxidase and iodothyronine deiodinase and their fns.Its 10 times weaker than thiomazole,so used during first trimester of pregnancy)
Use of propylthiouracil and thiomazole
Hyperthyroidism (Graves/ Bazedovs Disease)
SE of propylthiouracil
Allergic skin reactions, agranulocytosis
