Hypothyroidism: Difference between revisions
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**Cold intolerance, [[hypothermia]] | **Cold intolerance, [[hypothermia]] | ||
**Weight gain | **Weight gain | ||
**[[Weakness]] | **[[Weakness]] or fatigue | ||
**[[Lethargy]] | **[[Lethargy]] | ||
**Hoarse voice | **Hoarse voice | ||
Revision as of 14:54, 21 September 2022
Background
- 3-10x more common in females
- Peak incidence age >60
- Emergent manifestation of severe hypothyroid = myxedema coma
Etiology
- Primary
- Autoimmune (Hashimoto)
- Thyroiditis (subacute, silent, postpartum)
- Often preceded by hyperthyroid phase
- Iodine deficiency
- After ablation (surgical, radioiodine)
- After external radiation
- Infiltrative disease (lymphoma, sarcoid, amyloid, TB)
- Congenital
- Meds
- Amiodarone, lithium, iodine, Interferon-α, interleukin
- Idiopathic
- Secondary
- Panhypopituitarism
- Pituitary adenoma
- Infiltrative causes (e.g., hemochromatosis, sarcoidosis)
- Tumors impinging on the hypothalamus
- History of brain irradiation
- Infection (e.g., tuberculosis)
Spectrum of Thyroid Disease
- Myxedema coma << hypothyroidism < euthyroid > hyperthyroidism >> thyroid storm
Clinical Features
- Constitutional
- Cold intolerance, hypothermia
- Weight gain
- Weakness or fatigue
- Lethargy
- Hoarse voice
- Constipation
- Dysfunctional uterine bleeding
- Neuropsychiatric
- Delayed relaxation of DTRs
- Paresthesias
- Cardiopulmonary
- Bradycardia
- Hypoventilation
- Pericardial/pleural effusions
- Dermatologic
- Hair loss
- Non-pitting edema (periorbital, extremities)
- Facial swelling
Differential Diagnosis
- Addison's disease
- Chronic fatigue syndrome
- Constipation
- Depression
- Sick Euthyroidism
- Hypopituitarism
- Hypothermia
- Iodine Deficiency
Symptomatic bradycardia
- Cardiac
- Inferior MI (involving RCA)
- Sick sinus syndrome
- Neurocardiogenic/reflex-mediated
- Increased ICP
- Vasovagal reflex
- Hypersensitive carotid sinus syndrome
- Intra-abdominal hemorrhage (i.e. ruptured ectopic)
- Metabolic/endocrine/environmental
- Hyperkalemia
- Hypothermia (Osborn waves on ECG)
- Hypothyroidism
- Hypoglycemia (neonates)
- Toxicologic
- Infectious/Postinfectious
- Other
Evaluation
Work-up
- TSH
- Total and Free T4
- Total and Free T3
- Thyroid Binding Globulin (TBG)
- Auto-antibodies (anti-TPO, anti-microsomal, anti-Tg)
- Thyroid ultrasound
- ECG - bradycardia, low voltage
- VBG - hypercapnia from hypoventilation, possibly compensated if chronic
Categorization
| Type | Cause | TSH | FT4 |
| Primary | Failure of thyroid | Elevated | Low |
| Secondary | Failure of pituitary | Low | Low |
| Tertiary | Failure of hypothalamus |
Management
- Depends on etiology
- If treatment started, initiate low dose as daily doses too high may lead to thyroid storm
Primary (Central) Hypothyroidism
- Consider starting low dose levothyroxine at 25mcg daily
- Close follow-up with primary care or endocrinology
Subclinical Hypothyroidism
- TSH ≥10 mU/L
- Start low dose levothyroxine at 25mcg daily with close outpatient follow up
- Patients are at higher risk for atherosclerosis, myocardial infarction, and risk of progression to overt hypothyroidism
- The American Thyroid Association (ATA), American Association of Clinical Endocrinologists (AACE) and the European Thyroid Association guidelines recommend initiating treatment[1][2]
- TSH 7.0 to 9.9 mU/L
- <65 years old
- Start low dose levothyroxine at 25mcg daily with close outpatient follow up
- >65 years old
- Risk of over treatment vs. benefit is unclear[3]
- If patient has signs and symptoms of hypothyroidism, consider endocrinology consult prior to initiating treatment
- <65 years old
- TSH between upper limit of normal to 6.9 mU/L
- <65 years old
- Initiate low dose levothyroxine at 25mcg daily only if patient has signs and symptoms of hypothyroidism
- >65 years old
- May be normal for older age, do not initiate treatment
- Close outpatient follow-up for repeat labs
- <65 years old
Disposition
- Most hypothyroidism is treated as an outpatient
- Admit and treat severe hypothyroidism or myxedema coma
See Also
References
- ↑ Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid 2012; 22:1200.
- ↑ Pearce SH, Brabant G, Duntas LH, et al. 2013 ETA Guideline: Management of Subclinical Hypothyroidism. Eur Thyroid J 2013; 2:215.
- ↑ Mooijaart SP, Du Puy RS, Stott DJ, et al. Association Between Levothyroxine Treatment and Thyroid-Related Symptoms Among Adults Aged 80 Years and Older With Subclinical Hypothyroidism. JAMA 2019; 322:1977.