Hypothyroidism Flashcards
define hypothyroidism
underactive thyroid, low levels of thyroid hormone - T3/T4
who is most likely to be affected by hypothyroidism?
females more affected - esp with small stature at birth and low BMI in childhood
5 common causes of primary hypothyroidism
- autoimmune - Hashimoto’s thyroiditis
- lack of iodine in diet
- drugs - amiodarone, lithium, anti-epileptics
- any thyroiditis (thyroiditis has stages, in later stage pts are typically hypothyroidic)
- treatment of hyperthyroidism/
4 common secondary causes of hypothyroidism
- tumors on pituitary or hypothalamus
- drugs - dopamine, prednisone, or opiods
- Sheehand syndrome: pituitary necrosis after blood loss - mainly post childbirth
- radiation to the head area/cancer meds
whats a 3-step basic pathophys for primary hypothyroidism lab work
- thyroid cannot produce T4/T3
- low levels in body tell hypothalamus and pituitary to keep sending TRH and TSH
- increase in TSH, but low/no increase in free T4
why do we use free T4 as a lab measurement more often vs free T3?
we use free T4 more often because its a better representation of how well the thyroid is functioning to produce hormone as the majority of the thyroid produced by the thyroid is T4.
T4 also has a higher lifespan in the circulatory system so more likely to get a more accurate result
whats a 3-step basic pathophys for secondary/central hypothyroidism
- issue with pituitary gland or ability to release TRH to stimulate pituitiary
- decrease in TSH secretion
- decrease in T3/T4 hormone
what are the most common s/s for primary hypothyroidism?
- fluid retention/puffiness (periorbitally)
- tiredness
- cold intolerance
- mental fogginess
what are some key s/s for hypothyroidism (5)
- hair loss - outer 3rd of eyebrow
- periorbital myxedema
- goiter
- increased heaviness of menses
- constipation
what is a major, rare, and severe cx of hypothyroidism?
myxedema coma: severely low thyroid hormones ➔ pts basically in multiple organ failure, resp distress, hypothermia, altered mental status
what ix would you first order for a suspected thyroid issue
TSH
would be high in hypothyroidism
would you order a free T4 for hypothyroidism?
No, a TSH would be sufficient to be diagnostic of hypothyroidism
what antibodies would you test for for autoimmune causes of hypothyroidism (Hashimoto’s)
anti-thyroid peroxidase
anti-thyroglobulin antibodies
both would be positive in hypothyroidism
would you consider doing a thyroid u/s for hypothyroidism?
if i felt nodules
what other tests would you consider if a pt had confirmed Hashimoto’s thyroiditis?
other autoimmune disorder testing esp if there are s/s or there is a strong FH of other diseases
how do you tx hypothyroidism?
synthetic replacement
- first line: levothyroxine for LT treatment, esp because half life is longer
could consider liothyronine (T3 synth) would which be faster acting, but not as stable in the body, could be better suited in emergencies however, you would probs just use whichever med is most available
combination formulation ➔ desiccated thyroid hormone, however its naturally derived so there are always fluctuating amounts of T4/T3 in the med and not reliable for pts
