Hypothyroidism
Background
Affects ~4% US
3-10x more common in F
Peak incidence at age >60
More common among Caucasians, Latinos than AA
Types
- Primary: failure of thyroid
- elevated TSH, low FT4
- Secondary: failure of pituitary
- low TSH, low FT4
- Tertiary: failure of hypothalamus
Etiology
- Primary
- Autoimmune
- Idiopathic
- Postsurgical thyroidectomy
- External radiation therapy
- Radioiodine therapy
- Inherited enzymatic defect
- Iodine deficiency
- Antithyroid drugs
- Lithium, phyenylbutazone
- Secondary
- Pituitary tumor
- Infiltrative Dz (eg Sarcoid)
==DDx==
- Addisons disease
- anovulation
- autoimmune thyroid disease
- chronic fatigue syndrome
- craniopharyngiomas
- De Qeurvain Thyroiditis
- Depression
- Esoinophilia
- euthyroid sick syndrome
- fibromyalgia
- goiter
- hypochondriasis
- hypopituitarism
- hypothermia
- infectious mononucleosis
- iodine deficiency
- lithium nephropathy
- lymphoma
- ovarian insufficiency
- myxedema
- pituitary macroadenoma
- Prolactin deficiency
- SIADH
- thyroiditis
Work-Up
- TSH
- Total and Free T4
- T3
- Thyroid Binding Globulin (TBG)
- auto-antibodies (anti-TPO, anti-microsomal, anti-Tg)
- Ultrasound to look for nodules
Complications
Myxedema Coma ==Treatment==
Depends on etiology, consider starting Levothyroxine daily but be aware that doses too high may lead to thyroid storm
see Myxedema Coma ==Disposition==
- most hypothyroidism is treated as an outpatient followed in ambulatory clinic
- admit and treat sever hypothyroidism or myxedema coma
See Also
Endo: Myxedema Coma
Endo: Thyroid (General)
Source
Emedicine
Adapted from DeBonis