Overview
Hypothyroidism refers to underactivity of the thyroid, with reduced circulating thyroid hormones. This is usually accompanied by typical signs and symptoms of hypothyroidism.
Pathogenesis
Causes of Primary Hypothyroidism
Primary
- Autoimmune thyroiditis - Hashimoto's, atrophic
- Hypothyroid phase of thyroiditis
- Iatrogenic - radioiodine therapy, thyroidectomy, external irradiation of the neck
- Drugs - amiodarone, lithium, interferons, interleukin-2, iodide
- Iodine deficiency
- Thyroid infiltration - amyloidosis, tumour
- Congenital hypothyroidism
Secondary
- Pituitary / hypothalamic pathology - trauma, tumour, surgery, radiation, infection, infarction, infiltration
Manifestations
Clinical Features
Symptoms
- Weakness / lethargy / mental sluggishness
- Weight gain
- Cold intolerance
- Dry, coarse skin
- Constipation
- Menorrhagia
- Alopecia
Signs
- Bradycardia
- Psychomotor retardation
- Impaired cognition
- Cool, dry skin
- Facial oedema
- Loss of the outer 1/3 of the eyebrow
- Tongue enlargement
- Alopecia
- Hyporeflexia
- Non-pitting oedema
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