HYPOTHYROIDISM

               Dr. Mohamed Abo-Nar

Causes:

Primary:

• Congenital: absence of thyroid gland, ectopic thyroid remenant.
• Autoimmune: atrophic thyroiditis (most common - male: female = 6:1),Hashimoto's thyroiditis (mostly in middle age female), postpartum thyroiditis.
• Defect in hormone synthesis: iodine deficiency, antithyroid drugs (carbimazol).
• Infective: subacute thyroiditis.
• Post surgery.
• Post irradiation: radioactive iodine therapy, neck irradiation .
• Infiltirative: tumours.
• Prepheral resistance to thyroid hormone.

Secondary:

• Hypopitutarism.
• Isolated TSH deficiency.

Manifestation of Hypothyroidism:

• General manifestations; tiredness, weight gain, cold intolerance .
• Cardiovascular manifestations; bradycardia, angina .
• Neuromascular manifestations; muscle aches, pain (myalgia), carpal tunnel syndrome ,deafness , hoarseness of voice , depression and psychosis.
• Skin manifestations; dry skin ,oedema ( myxoedema), erythema, vitilligo,brittle hair.
• Reproductive manifestations; infertility, menorrhagia and galactorrhea.
• GIT manifestations; constipation .
• Blood manifestations; anaemia (normocytic or macrocytic)

Investigations :

• TSH is high in primary hypothyroidism ( test of choice).
• Total and free T4 are low ( T3 remain normal for long time).
• Thyroid and other organ specific anibodies may be present.
• Other findings; Anaemia, hyponatraemia, hyperchloesterolaemia .

Treatment :

• Thyroxine (T4) for life, starting dose 100ug/day in young but in old startwith 50 ug/day.
• If hypopitutarism is suspected , hydrocortisone replacement should start first.