Thyroid Dysfunction Flashcards
Hypothyroidism
More common- esp in older women. Develops slowly.
Hyperthyroidism
develops acutely- comes on faster and easier to diagnose.
Goitre
when the thyroid becomes enlarged which can happen under both
hypo and hyperthyroidism
Symptoms for hypothyroidism (underactive)
Slower metabolism causes cold intolerance
Dry, pale, cool skin
Yellowish skin
Puffy skin
Slower body systems causing fatigue weakness and depression
High cholesterol
Weight gain with decreased appetite
Bradycardia
Symptoms for hyperthyroidism (overactive)
Increased metabolism causes increased heart rate and BP
Weight loss but an increased appetite
Heat intolerance
Sweating and warm, moist skin
Nervousness and tremors
Tachycardia
Primary hypothyroidism
In the thyroid gland
In most clinical situations, unless specifically mentioned, hypothyroidism refers to primary hypothyroidism.
Secondary hypothyroidism
Where the defect is not in the thyroid gland.
Sporadic
Critical causes of primary hypothyroidism
Cogenital (childhood)- if untreated leads to cretinism
Acquired (adult)- hashimotos thyroiditis (autoimmune and most common in west)
Drug induced- commonly amiodaron and lithium. following surgery and radioactive iodine treatment of thyrotoxicosis.
Iodine deficiency- most common worldwide but rare in west
Critical causes of secondary hypothyroidism
Hypothalamic and pituitary diseases
TSH deficiency
Thryoid function tests
Most important- TSH (thyrotropin level). In primary, TSH levels will be high, but thyroid hormone will be low.
Measuring free T3 (FT3) and T4 (FT4) is more direct but also more expensive and difficult- thryoid hormones highly plasma protein bound.
First line treatment hypothyroidism
Replacement therapy with synthetic thyroid hormones.
Thyroxine/levothyroxine
o Orally active and cheap. Takes a long time to achieve steady state and therefore dose adjustment is made only after 3-4 weeks
Second line treatment hypothyroidism
Triiodothyronine (Official name: liothyronine)
Can be given orally or IV. Quicker action but only advantageous in severe hypothyroid cases; may cause wide fluctuation in plasma concentration between doses.
Why does it usually take months to finalise required doses for new pt?
thyroxine has a half-life of about a week and hence (as you might have come across in pharmacokinetics study) it takes 4-5 weeks to reach a steady-state plasma concentration
Hypothyroidism medication potential side effects
Thyroid hormone has a disproportionately higher activity in the cardiovascular system and in particular the heart.
As hypothyroidism mainly affects older people, it is possible that the patient might suffer from subclinical cardiac conditions (such as angina and myocardial infraction) which can be precipitated by a high initial dose of thyroxine.
