Hypothyroidism: Difference between revisions
 
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==Background==
==Background==
#Affects ~4% US
*3-10x more common in females
#3-10x more common in F
*Peak incidence age >60
#Peak incidence at age >60
*Emergent manifestation of severe hypothyroid = [[myxedema coma]]
#More common among Caucasians, Latinos than AA


==Types==
===Etiology===
#Primary: failure of thyroid
*Primary
##elevated TSH, low FT4
**Autoimmune (Hashimoto)
#Secondary: failure of pituitary
**[[Thyroiditis]] (subacute, silent, postpartum)
##low TSH, low FT4
***Often preceded by hyperthyroid phase
#Tertiary: failure of hypothalamus
**Iodine deficiency
**After ablation (surgical, radioiodine)
==Etiology==
**After external radiation
# Primary
**Infiltrative disease (lymphoma, sarcoid, amyloid, [[TB]])
## Autoimmune
**Congenital
## Idiopathic
**Meds
## Postsurgical thyroidectomy
***[[Amiodarone]], [[lithium]], iodine, [[Interferon-α]], interleukin
## External radiation therapy
**Idiopathic
## Radioiodine therapy
*Secondary
## Inherited enzymatic defect
**Panhypopituitarism
## Iodine deficiency
**Pituitary adenoma
## Antithyroid drugs
**Infiltrative causes (e.g., [[hemochromatosis]], [[sarcoidosis]])
## Lithium, phyenylbutazone
**[[brain tumor|Tumors]] impinging on the hypothalamus
# Secondary
**History of brain irradiation
## Pituitary tumor
**Infection (e.g., [[tuberculosis]])
## Infiltrative Dz (eg Sarcoid)  


==DDx==
{{Thyroid gen background}}
# 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 (Main) | Ultrasound]] to look for nodules


==Complications==
==Clinical Features==
[[Myxedema Coma]]
*Constitutional
**Cold intolerance, [[hypothermia]]
**Weight gain
**[[Weakness]] or fatigue
**[[Lethargy]]
**Hoarse voice
**[[Constipation]]
**Dysfunctional [[vaginal Bleeding (Non-Pregnant)|uterine bleeding]]
*Neuropsychiatric
**Delayed relaxation of DTRs
**[[Paresthesias]]
*Cardiopulmonary
**[[Bradycardia]]
**Hypoventilation
**[[pericardial effusion|Pericardial]]/[[pleural effusions]]
*Dermatologic
**Hair loss
**Non-pitting edema (periorbital, extremities)
**Facial swelling


==Treatment==
==Differential Diagnosis==
#Depends on etiology, consider starting Levothyroxine daily but be aware that doses too high may lead to thyroid storm
*[[Addison's disease]]
#see Myxedema Coma
*Chronic fatigue syndrome
*[[Constipation]]
*[[Depression]]
*Sick Euthyroidism
*Hypopituitarism
*[[Hypothermia]]
*Iodine Deficiency
 
{{Symptomatic bradycardia}}
 
==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===
{| {{table}}
| align="center" style="background:#f0f0f0;"|'''Type'''
| align="center" style="background:#f0f0f0;"|'''Cause'''
| align="center" style="background:#f0f0f0;"|'''TSH'''
| align="center" style="background:#f0f0f0;"|'''FT4'''
|-
| Primary||Failure of thyroid||Elevated||Low
|-
| Secondary||Failure of pituitary||Low||Low
|-
| Tertiary||Failure of hypothalamus
|}
 
[[File:thyroid studies.JPG|px200]]
 
==Management==
*Depends on etiology <ref>Ross D. Treatment of primary hypothyroidism in adults. In: UpToDate, UpToDate, Waltham, MA. (Accessed on September 21, 2022.)</ref><ref>Ross D. Subclinical hypothyroidism in nonpregnant adults. In: UpToDate, UpToDate, Waltham, MA. (Accessed on September 21, 2022.)</ref>
*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<ref>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.</ref><ref>Pearce SH, Brabant G, Duntas LH, et al. 2013 ETA Guideline: Management of Subclinical Hypothyroidism. Eur Thyroid J 2013; 2:215.</ref>
 
*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<ref>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.</ref>
***If patient has signs and symptoms of hypothyroidism, consider endocrinology consult prior to initiating treatment
 
*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


==Disposition==
==Disposition==
# most hypothyroidism is treated as an outpatient followed in ambulatory clinic
*Most hypothyroidism is treated as an outpatient
# admit and treat severe hypothyroidism or myxedema coma
*Admit and treat severe hypothyroidism or [[myxedema coma]]


==See Also==
==See Also==
*[[Myxedema Coma]]
*[[Myxedema coma]]
*[[Thyroid (General)]]
*[[Thyroid (Main)]]
 
==Source==
Emedicine.


Adapted from DeBonis
==References==
<References/>


[[Category:Endo]]
[[Category:Endocrinology]]

Latest revision as of 18:10, 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
    • Idiopathic
  • Secondary

Spectrum of Thyroid Disease

Thyroid physiology: Hypothalamus (top) releases TRH; causing pituitary gland (second from top) to release TSH; causing thyroid gland (third from top) to make T3 and T4; inhibition loops also shown.

Clinical Features

Differential Diagnosis

Symptomatic bradycardia

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

px200

Management

  • Depends on etiology [1][2]
  • 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[3][4]
  • 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[5]
      • If patient has signs and symptoms of hypothyroidism, consider endocrinology consult prior to initiating treatment
  • 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

Disposition

  • Most hypothyroidism is treated as an outpatient
  • Admit and treat severe hypothyroidism or myxedema coma

See Also

References

  1. ↑ Ross D. Treatment of primary hypothyroidism in adults. In: UpToDate, UpToDate, Waltham, MA. (Accessed on September 21, 2022.)
  2. ↑ Ross D. Subclinical hypothyroidism in nonpregnant adults. In: UpToDate, UpToDate, Waltham, MA. (Accessed on September 21, 2022.)
  3. ↑ 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.
  4. ↑ Pearce SH, Brabant G, Duntas LH, et al. 2013 ETA Guideline: Management of Subclinical Hypothyroidism. Eur Thyroid J 2013; 2:215.
  5. ↑ 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.
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