Physiology
The more potent thyroid hormone
Triiodothyronine (T3)
Drug of choice for hypothyroidism treatment
Levothyroxine
Initial adult levothyroxine dose <65y.o.
1.5- 1.8 mcg/kg/day
2 definitive treatments of hyperthyroidism
Surgery and radioactive iodine ablation
what are bone (osteoclastic activity) kidney (calcium resorption in the proximal tubule) and intestines (calcium absorption due to increased vitamin D from kidney)
The type of T4 we measure
Free T4
Brand name for liothyronine
Cytomel
Initial geriatric levothyroxine dosing
12 - 50mcg per day
1 Advantage and 1 disadvantage of thionamides
Less invasive, chance of sustained remission, avoidance of permanent hypothyroidism
Difficult to titrate, agranulocytosis, vasculitis, hepatotoxicity
This is the first test to order when a BMP shows hypercalcemia
The other name for T4
Thyroxine
Autoimmune disease that cause hypothyroidism
Hashimoto's Disease
Initial neonatal levothyroxine dose
10 - 15mcg/kg/day
Due to systemic autoantibodies, this complication of cured hyperthyroidism persists
Of ionized calcium, PTH, and vitamin D, this test is always high in primary hyperparathyroidism, and low and secondary hyperparathyroidism
What is ionized calcium?
The name of the axis involved in thyroid function
Hypothalamic-Pituitary-Thyroid (HPT) axis
Most severe clinical presentation of hypothyroidism
Myxedema Coma
Ideal time to recheck TSH after initiating levothyroxine
6 weeks
Medications for Thyroid Storm
beta blockers
iodinated contrast
PTU or methimazole
cholestyramine
glucocorticoids
Any of these are indications for surgical management of primary hyperparathyroidism.
<50y.o.
ionized calcium >1mg/dL high
osteoporosis
CRI or nephrolithiasis
symptoms
Normal levels of TSH (per guidelines)
Lower limit: 0.3 or 0.4
Upper limit: 4.5 or 5.0
Lithium, amiodarone, guaifenesin, iodinated contrast, kelp tablets, thalidomide
Estrogen's effect on levothyroxine dose requirement
Increases
- predictably in pregnancy
- mildly with exogenous administration
- menopause and transgender females
Preferred thionamide in the first trimester
PTU
osteoporosis: bisphosphonates
hypercalcemia: calcimimetics
vitamin d deficiency
nephrolithiasis: thiazide diuretics