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Essentials of Diagnosis
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Autoimmune (Hashimoto) thyroiditis is the most common cause of hypothyroidism.
Fatigue, cold intolerance, constipation, weight change, depression, menorrhagia, hoarseness.
Dry skin, bradycardia, delayed return of deep tendon reflexes.
FT4 is usually low.
TSH elevated in primary hypothyroidism
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General Considerations
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Primary hypothyroidism is due to thyroid gland disease
Secondary hypothyroidism is due to deficiency of pituitary TSH
Maternal hypothyroidism during pregnancy results in cognitive impairment in child
Goitrogenic medications include
Chemotherapeutic agents that can cause silent thyroiditis include
Tyrosine kinase inhibitors
Denileukin diftitox
Alemtuzumab
Interferon-α
Interleukin-2
Thalidomide, lenalidomide
Immune checkpoint inhibitors
Radiation therapy to the head-neck-chest-shoulder region can cause hypothyroidism with or without goiter or thyroid cancer many years later
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Differential Diagnosis
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Serum TSH is increased in primary hypothyroidism
Serum FT4 may be low or low normal
Other laboratory abnormalities include
Hyponatremia due to SIADH or decreased glomerular filtration rate is common
Additional findings frequently include increased serum levels of
During pregnancy in women with hypothyroidism taking replacement thyroxine, check serum TSH frequently (eg, every 4–6 weeks) to ensure adequate replacement
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