Hypothyroidism

Revision as of 15:38, 18 July 2017 by Mmir (talk | contribs) (→‎Overview)
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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

Overview

Environmental iodine deficiency is the most common cause of hypothyroidism on a worldwide basis (16). In areas of iodine sufficiency, such as the United States, the most common cause of hypothyroidism is chronic autoimmune thyroiditis (Hashimoto’s thyroiditis).Autoimmune thyroid diseases (AITDs) have been estimated to be 5-10 times more common in women than in men.

Symptom and signs of hypothyroidism is mostly related to the magnitude of the thyroid hormone deficiency, and the acuteness with which the deficiency develops rather than the cause of hypothyroidism. However, the typical clinical manifestations of hypothyroidism may vary depending on the origin of the disease. Patient clinical manifestations- if associated with secondary and tertiary hypothyroidism, may present other coexisting endocrine deficiencies such as hypogonadism and adrenal insufficiency, that may mask the manifestations of hypothyroidism. Although hypothyroidism diagnosis is mainly a laboratory diagnosis, the coexisting conditions and wide variation in clinical presentation may make the diagnosis harder.

Classification

The table below presents a classification of isolated thyroid disorders and its causes based on the classification:

Origin of the defect Causes
Endagenous causes Exagenous causes
Thyroid Pituirtary Hypothalamus Surgery or radiation Other causes
Primary hypothyroidism + - -
Transient hypothyroidism + + -
  • Major surgeries
Central Hypothyroidism Secondary

OR

Pituitary originated

- + -
Tertiary

OR

Hypothalamus originated

- - +

Classification of thyroiditis based on the duration algorythm

 
 
 
 
 
 
 
 
 
 
 
 
History, signs, and symptoms suggestive of hypothyroidism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Measure FT4 and TSH
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Normal FT4, Elevated TSH>5.5
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Decresased level of FT4
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Subclinical hypothyroidism
 
 
 
 
 
 
 
 
 
 
Elevated TSH > 5.5
 
 
 
 
 
 
 
 
 
 
 
Normal TSH level OR Decreased TSH level < 0.2
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Check anti-thyroid autoantibodies and TPOAb
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Check TRH
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Increased
 
 
 
 
 
 
 
Normal
 
 
 
 
 
 
 
 
Normal or increased
 
 
 
 
 
 
 
Decreased
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Autoimmune thyroiditis
• Resistance to TSH
 
 
 
 
 
 
 
Iodine deficeincy
Thyroiditis
 
 
 
 
 
 
 
 
•Pituitary related hypothyroidism
 
 
 
 
 
 
 
•Hypothalamus related hypothyroidism

Differential diagnosis

Disease History and symptoms Laboratory findings Additional findings
Fever Goiter Pain TSH Free T4 T3 T3RU Thyroglobin TRH TPOAb
Primary hypothyroidism Autoimmune + +/-

Diffuse

- N/ Normal N/ Normal
  • May be accompanied by other autoimmune diseases
Thyroiditis + +/- + Normal Normal N/ Normal Normal
  • Infectious thyroiditis associated with neck pain
Others - +/- - Normal Normal N/ Normal Normal
  • History of hyperthyroiditis
  • Drug history
Transient hypothyroidism +/- - +/- Normal Normal Normal Normal
  • May present primarily with hyperthyroiditis
Subclinical hypothyroidism - - - Normal Normal Normal Normal N/
  • Asymptomatic
Central Hypothyroidism Pituitary + - - N/ N/ N/ Normal Normal Normal
  • Other pituitary hormone deficiencies signs
Hypothalamus + - - Normal Normal
  • Other pituitary hormone deficiency signs
Resistance to TSH/TRH - - - N/ N/ Normal Normal / Normal
  • Rare

History and symptoms

Symptoms Constituitional HEENT Neuromuscular Complications
More common
Less common
  • Slowed speech and movements