Hypothyroidism Flashcards

1
Q

Clinical Features

A

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

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2
Q

D/Dx of high TSH (primary vs. secondary hypothyroidism)

A
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

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3
Q

Risk Factors

A

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

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4
Q

Screening

A

No evidence to screen asymptomatic patients
Controversial to screen prior to pregnancy or when confirmed pregnant
Previous thyroid disease
Previous radiation
Pituitary / hypothalamic disorder

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5
Q

Investigations: how to distinguish between primary vs. central hypothyroidism

A
TSH high (>4-5mU/L) - Possible Primary Hypothyroidism
↑TSH + ↓free T4 = primary hypothyroidism 
↓TSH + ↓free T4 = central hypothyroidism
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6
Q

Labs if suspicious of infiltrative, Riedel’s, subacute granulomatous thyroiditis

A

Thyroid Peroxidase Antibody (Anti-TPO Ab) + Thyroglobulin + Thyrotropin receptor antibody

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7
Q

Additional Labs to consider

A

Hgb + MCV (macrocytosis), Lytes (hyponatremia), Triglycerides (hyperlipidemia), CK (increased)

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8
Q

Indications to treat / not to treat subclinical hypothyroidism. How long do you monitor for?

A

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

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9
Q

Indications for treatment

A

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)

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10
Q

First line treatment, how often it is titrated, treatment targets, expected length of treatment before results are seen

A

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

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11
Q

How is thyroxine absorption affected? Give 3 examples of each.

A

thyroxine absorption affected by certain foods (high fiber, soy, coffee) and meds (cholestyramine, calcium, iron, antacids, PPI, anticonvulsants)

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12
Q

When is thyroxine best taken? When should other medications be taken?

A

Take thyroxine 30 min before breakfast on empty stomach

Take any meds that interfere with thyroxine 2 hrs after

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13
Q

If concerns for compliance, when / how should thyroxine be taken?

A

If issues with compliance, take entire weeks dose once per week

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14
Q

How often / when should TSH be repeated?

A

Repeat TSH 6-8 weeks after starting dose and q6-8 weeks until in target
Repeat yearly once stable

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15
Q

When should TSH be followed?

A

Follow serum TSH when started on medications, change in body weight, aging, pregnancy

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16
Q

Indications for consultation

A

CAD, arrythmia, central hypothyroidism, myxedema coma