Hypothyroidism Flashcards
Clinical Features
General: Fatigue/Lethargy, Cold intolerance
Cognitive: Depression, Memory, Sleep Disturbance
HEENT: Macroglossia, hoarseness, goitre
CVS: bradycardia, pericardial effusion, HTN, CHF, Angina
Resp: decreased exercise capacity, muscle weakness, sleep apnea
GI: Constipation, weight gain, decreased appetite
Neuro: Paresthesias, muscle cramps, delayed relaxation of deep tendon reflexes, carpel tunnel
GU: Menstrual irregularities, Impotence
Derm: periorbital edema, Dry skin, coarse hair, thinned eyebrows (lateral 1/3), brittle nails
Heme: Anemia
D/Dx of high TSH (primary vs. secondary hypothyroidism)
Primary Hypothyroidism:
Drugs: Amiodarone, Lithium, Iodine
Hashimoto’s
Post Partum Thyroiditis
Iodine Deficiency
Infiltrative
Agenesis / Dysgenesis of thyroid
Secondary Hypothyroidism:
Pituitary Adenoma
Pituitary Damage: tumor, mets, hemorrhage, necrosis, aneurysm, sx, trauma
Infiltrative: Sarcoidosis, TB, Granulomatous Disease
Risk Factors
Female
Age > 45-50
PMHx: Autoimmune disease (T1DM, adrenal insufficiency, celiac, RA, SLE, vitiligo), Prior neck irradiation
FMHx: Thyroid Dx, autoimmune Dx
OBGYN: Pregnant during 1st Trimester, Postpartum (6 weeks to 6 months)
Meds: Amiodarone, Lithium, Iodine
Screening
No evidence to screen asymptomatic patients
Controversial to screen prior to pregnancy or when confirmed pregnant
Previous thyroid disease
Previous radiation
Pituitary / hypothalamic disorder
Investigations: how to distinguish between primary vs. central hypothyroidism
TSH high (>4-5mU/L) - Possible Primary Hypothyroidism
↑TSH + ↓free T4 = primary hypothyroidism
↓TSH + ↓free T4 = central hypothyroidism
Labs if suspicious of infiltrative, Riedel’s, subacute granulomatous thyroiditis
Thyroid Peroxidase Antibody (Anti-TPO Ab) + Thyroglobulin + Thyrotropin receptor antibody
Additional Labs to consider
Hgb + MCV (macrocytosis), Lytes (hyponatremia), Triglycerides (hyperlipidemia), CK (increased)
Indications to treat / not to treat subclinical hypothyroidism. How long do you monitor for?
Treat w/ Levothyroxine if:
Elevated thyroid peroxide antibodies (TPO)
Goiter
Strong Family Hx of Autoimmune Disorder
Pregnancy (trying to get pregnant or very high risk pregnancy)
NO treatment if TSH <10, normal T4, asymptomatic, not pregnant
BMJ Guideline 2019 – no tx if TSH <20 w/ normal T4
Monitor q 12 mo
Indications for treatment
Txt if TSH > 10 + Symptomatic
Txt if TSH 5-10 AND
Elevated thyroid peroxide antibodies (TPO)
Goiter
Strong Family Hx of Autoimmune Disorder
Pregnancy (trying to get pregnant or very high risk pregnancy)
First line treatment, how often it is titrated, treatment targets, expected length of treatment before results are seen
Levothyroxine start 12.5-50mcg/day
Titrate 12.5 mcg q4-6 weeks until TSH is at target
(takes 8-12 weeks for TSH equilibrium after dose change
Target TSH euthyroid range (except in secondary hypothyroidism, where target FT4)
Improves sxs in ~2w, complete recovery in months
How is thyroxine absorption affected? Give 3 examples of each.
thyroxine absorption affected by certain foods (high fiber, soy, coffee) and meds (cholestyramine, calcium, iron, antacids, PPI, anticonvulsants)
When is thyroxine best taken? When should other medications be taken?
Take thyroxine 30 min before breakfast on empty stomach
Take any meds that interfere with thyroxine 2 hrs after
If concerns for compliance, when / how should thyroxine be taken?
If issues with compliance, take entire weeks dose once per week
How often / when should TSH be repeated?
Repeat TSH 6-8 weeks after starting dose and q6-8 weeks until in target
Repeat yearly once stable
When should TSH be followed?
Follow serum TSH when started on medications, change in body weight, aging, pregnancy
