Function of the thyroid gland
secrete hormones which control metabolic pathways and numerous physiological functions
produces thyroxine (T4) and triodothyronine (T3)
active form of thyroid hormone
T3
Normal range for TSH
0.4-4.0 mIU/L
Normal range for T4
4.5-11.2 mcg/dL
Normal range for T3
100-200 ng/dL
S/S of hyperthyroidism
Nervousness
Anxiety
Palpitations
Emotional lability
Easy fatigability
Menstrual disturbances
Heat intolerance
Weight loss with increase appetite
Warm, smooth, moist skin
Exophthalmos
Pretibial myxedema
Unusually fine hair
Onycholysis
Retraction of the eye
Clinical presentation/diagnosis of hyperthyroidism
low TSH serum concentration < 0.1
elevated T3 & T4
elevated radioactive iodine uptake
An autoimmune syndrome that includes hyperthyroidism, diffuse thyroid enlargement, exophthalmus, pretibial myxedema, thyroid acropachy
Graves' Disease
Treatment for thyrotoxic periodic paralysis, a rare condition associated with hypokalemia and Graves' Disease
K+ supplement
Propranolol
Spironolactone
Drug-induced hyperthyroidism can be caused by:
Amiodarone
Lithium
Interferon alpha
IL-2 agents
Over-supplementation with thyroid hormone
Antithyroid medications, MOA, doasage...
Methimazole
- Inhibit coupling of MIT and DIT to form T4 and T3
- 10x more potent than PTU
- first line
- daily maintenance: 5-30 mg/day
Propylthiouracil (PTU)
- Inhibit coupling of MIT and DIT to form T4 and T3
- Inhibits peripheral conversion of T4 to T
Monitoring required once a hyperthyroid patient is in remission
follow up every 6-12 months once in remission
if relapse occurs, start radioactive iodine
do NOT re-start antithyroid meds
1st line treatment for hyperthyroidism in pregnancy
1st trimester: PTU is 1st line due to possible birth defects with MMI
2nd or 3rd trimester: MMI is 1st line due to hepatotoxicity with PTU
Adverse effects with PTU & MMI
Minor:
Pruritic maculopapular rashes
arthralgias
fever
Major:
benign transient leukopenia
agranulocytosis
congenital malformations - with MMI
hepatotoxicity - with PTU
If adverse effects occur with 1 antithyroid med, can the pt switch to another?
Switch if the adverse effects are minor
Don't switch if adverse effect is major
MOA of Iodides
Acutely block thyroid hormone release
Inhibit thyroid hormone biosynthesis
Decrease the size of the gland
- Large doses may exacerbate hyperthyroidism
- Contraindicated in multinodular goiter (MNG)
Side effects of iodides
Hypersensitivity
Salivary gland swelling
Iodism
Gynecomastia
Side effects of potassium iodide
Hypersensitivity
Salivary gland swelling
Iodism
Gynecomastia
Main adrenergic blockers used as adjunctive therapy with antithyroid drugs, RAI or iodides
Propranolol
Nadolol - if patient has asthma or COPD bc it's cardioselective
Why are antithyroid medications given to pts prior to RAI?
because RAI may cause an initial increase in T3 and T4
1st line therapy for neonatal and pediatric hyperthyroidism
MMI 0.5 mg/kg/day
What should be used to treat fever associated with thyroid storm?
acetaminophen
NEVER use aspirin or NSAIDs
1st line beta blocker for emergency use for thyroid storm
esmolol
- short-acting, effects can be easily reversed
- safe in pulmonary disease
- safe in CV disease
S/S of hypothyroidism
Dry skin
Cold intolerance
Weight gain
Constipation
Weakness
Lethargy
Depression
Muscle cramps
Infertility
Coarse skin and hair
Cold or dry skin
Periorbital puffiness
Bradycardia
Slow speech
Reversible neurologic syndromes
Clinical presentation/diagnosis of hypothyroidism
elevated TSH serum concentration
decreased T3 and T4 serum concentrations
drug of choice for hypothyroidism
Levothyroxine because it's chemically stable, inexpensive, and has uniform potency
Drugs that can decrease effect of levothyroxine
Cholestyramine, calcium carbonate, sucralfate, aluminum hydroxide, espresso coffee, ferrous sulfate, H2 blockers, PPIs, rifampin, carbamazepine, and possibly phenytoin
ingestion with food can impair absorption
weight and age based dosage of levothyroxine
weight based dose: 1.7 mcg/kg/day
older pt. w/ CV disease: start on 25 mg/day
older pt. without CV disease: start on 50 mg/day
Most sensitive and specific parameter to measure for monitoring
TSH level - check every 6 weeks
What drugs can suppress the concentration of TSH?
dopamine
dopaminergic agents (bromocriptine)
somatostatin or somatostatin analogs (octreotide)
corticosteroids
T4 level can be used to assess:
noncompliance
malabsorption
changes in levothyroxine product bioequivalence
treatment for congenital hypothyroidism
start maintenance therapy early - within 45 days of birth
levothyroxine dose of 10-15 mcg/kg/day then titrate down
treatment for hypothyroidism in pregnancy
levothyroxine
effects of hypothyroidism on selected medications
digitalis preparations
insulin
warfarin
respiratory depressants:
barbiturates
phenothiazines
opioid analgesics