Hypothyroidism

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Hypothyroidism Main page
Patient Information
Overview
Classification Primary hypothyroidism Hashimoto's thyroiditis Secondary hypothyroidism Tertiary hypothyroidism
Differentiating different causes of hypothyroidism
Screening
Diagnosis
History and symptoms

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2]

Synonyms and keywords: Myxedema; myxoedema; thyroid activity decreased; hypothyroid

Classification

	Origin of the defect			Causes
				Endagenous causes	Exagenous causes
	Thyroid	Pituirtary	Hypothalamus		Surgery or radiation	Other causes
Primary hypothyroidism	+	-	-	Congenital hypothyroidism Autoimmune (Hashimoto's) thyroiditis	Thyroidectomy Radioiodine therapy	Iodine deficeincy Drug induced thyroiditis Amiodarone Lithium Thionamide Iodine Iterferon Sunitinib Rifampicin Thalidomide
Transient hypothyroidism	+	+	-	Subacute (de Quervain’s) thyroiditis Postpartum thyroiditis
Secondary hypothyroidism	-	+	-	Pituitary mass lesions, especially pituitary adenomas Brain cysts and abscesses meningiomas dysgerminomas metastatic tumors craniopharyngiomas pituitary apoplexy Sheehan syndrome (postpartum pituitary necrosis) Idiopathic isolated TSH deficiency	surgery of pituitary adenomas radiation therapy pituitary adenomas other mass lesions near pituitary gland	head trauma with injury of the stalk
Tertiary hypothyroidism	-	-	+	hemochromatosis histiocytosis autoimmune lymphocytic hypophysitis Developmental abnormalities internal carotid aneurysms Other central nervous system (CNS) tumors Idiopathic isolated TRH deficiency	Radiation in high doses to the brain infratemporal nasopharyngeal oropharyngeal	Infections tuberculosis syphilis toxoplasmosis sarcoidosis

hei

• Primary hypothyroidism
  • Congenital hypothyroidism
  • Autoimmune (Hashimoto's) thyroiditis
  • Iodine deficeincy
  • Drug induced thyroiditis
    • Amiodarone
    • Lithium
    • Thionamide
    • Iodine
    • Iterferon
    • Sunitinib
    • Rifampicin
    • Thalidomide
  • Thyroidectomy
  • Radioiodine therapy
• Transient hypothyroidism
  • Subacute (de Quervain’s) thyroiditis
  • Postpartum thyroiditis

• Secondary hypothyroidism (due to decreased levels of TSH)
  • Pituitary mass lesions, especially pituitary adenomas
  • cysts and abscesses
  • meningiomas
  • dysgerminomas
  • metastatic tumors
  • craniopharyngiomas
  • surgery or radiation therapy for pituitary adenomas or other mass lesions near pituitary gland
  • head trauma with injury of the stalk
  • pituitary apoplexy
  • Sheehan syndrome (postpartum pituitary necrosis)
  • Idiopathic isolated TSH deficiency

• Tertiary hypothyroidism
  • Infiltrative disorders affecting the pituitary or the hypothalamus include hemochromatosis, and histiocytosis
  • autoimmune lymphocytic hypophysitis
  • Developmental abnormalities
  • internal carotid aneurysms
  • Other central nervous system (CNS) tumors
  • Idiopathic isolated TRH deficiency

Differential diagnosis

Disease		History and symptoms					Laboratory findings								Additional findings
		Fever	Goiter				TSH	Free T4	T3	T3RU	Thyroglobin	TRH	C-peptide level	Serum glucagon
Primary hypothyroidism		+	+	+	+	-	↑	↓	Normal or ↓	Normal	N/↑	Normal	↓	Normal	Auto antibodies present (Anti GAD-65 and anti insulin anti bodies)
Transient hypothyroidism		+	+	+	+	-	↑	↑	Normal	Normal	↑	Normal	Normal	↑	Acanthosis nigricans
Subclinical hypothyroidism		+	+	+	-	+	↑	Normal	Normal	Normal	↑	Normal	Normal	N	-
Central Hypothyroidism	Pituitary	+	+	-	-	-	Normal or ↓	Normal or ↓	Normal or ↓	↓	Normal	Normal	Normal	Normal	-
	Hypothalamus	+	+	-	-	-				↑	Normal	Normal	Normal	Normal	-
Transient hyperglycemia		-	-	-	-	-	↑	↑	Normal	Normal	↑	Normal	Normal	N/↑	In hospitalized patients especially in ICU and CCU
Steroid therapy		+	-	-	-	+	↑	↑	Normal	Normal	↑	↑	N/↑	N/↑	Acanthosis nigricans,
RTA 1		-	-	-	+	-	Normal	Normal	↑	Normal	↑	Normal	Normal	Normal	Hypokalemia, nephrolithiasis
Glucagonoma		-	-	-	-	-	↑	Normal	Normal	Normal	-	Normal	Normal	↑	Necrolytic migratory erythema
Cushing syndrome		-	-	-	-	+	↑	-	Normal	↓	N/↑	↑	Normal	Normal	Moon face, obesity, buffalo hump, easy bruisibility

General feature

Symptoms

	Constituitional	Local	Reproductive	Neuropsysiological	Others	Physical exam
	cold intolerance puffiness decreased sweating coarse skin hypothermia Fever if accompanied by thyroiditis weight gain coarse, brittle, straw like hair with hair loss	obstructive sleep apnea (secondary to macroglossia)	Females can present with galactorrhea and menstrual disturbances	depression	paresthesia and nerve entrapment syndromes	decreased systolic blood pressure increased diastolic blood pressure bradycardia pericardial effusion abdominal distension ascites (uncommon) non-pitting edema (myxedema) pitting edema of lower extremities hyporeflexia with delayed relaxation ataxia
		fullness and pain in the throat and neck	infertility	emotional lability	constipation
		hoarseness sore throat		blurred vision	macroglossia
		goiter		Attention deficit	periorbital puffiness
				slowed speech and movements

• Metabolic abnormalities associated with hypothyroidism include:
  • anemia,
  • dilutional hyponatremia,
  • hyperlipidemia,
  • reversible increase in creatinine

Complications

Myxedema coma

Rare, severe form of hypothyroidism, a life-threatening condition

• Altered mental status,
• hypothermia,
• bradycardia,
• hypercarbia, and
• hyponatremia.
• Cardiomegaly,
• pericardial effusion,
• cardiogenic shock, and
• ascites
• commonly occurs in individuals with undiagnosed or untreated hypothyroidism who is subjected to an external stress, such as low temperature, infection, or medical intervention (e.g., surgery or hypnotic drugs)