Hypothyroidism

Introduction

Hypothyroidism is a condition associated with reduction in thyroid hormone production.
Thyroid hormone is required for normal metabolism and growth.
Its deficiency has major consequences on foetal development as well as intellectual and physical development in infants and children (cause of cretinism).
In adults, it may be the cause of several problems including heart disease, menstrual irregularity and infertility, mental health conditions and dementia.
lodine replacement is not the treatment for hypothyroidism.
Screening for hypothyroidism in all new borns, and every 5 years in adults after age 35 years, especially females, by measuring TSH (thyroid stimulating hormone) levels in blood where this is possible, should be encouraged.

Causes of hypothyroidism

The causes of hypothyroidism include the following

  • Antibody-related thyroid gland destruction
  • Subtotal thyroidectomy
  • Pituitary surgery or lesions
  • Congenital
  • Severe iodine deficiency
  • Drug induced (e.g. radioiodine therapy, amiodarone etc.)

Symptoms of hypothyroidism

The following are the symptoms of hypothyroidism

  1. General weakness and tiredness
  2. Intolerance to cold environments
  3. Constipation
  4. Weight gain
  5. Hair loss.
  6. Dry skin
  7. Hoarse voice
  8. Memory loss
  9. Goitre may be present
  10. Abnormal menstrual periods and sub-fertility (in adult females)
  11. Poor growth, development and poor school performance in children

Signs of hypothyroidism

Signs in neonateĀ 

  1. Prolonged neonatal jaundice
  2. Excessive sleep
  3. Feeding problems

Signs in children

  1. Cretinism (mental subnormality, short stature, large tongue, dry skin, sparse hair, protuberant abdomen, umbilical hernia, abnormal facies)

Signs in adults

  1. Slow pulse (usually <60 per minute)
  2. Dry coarse skin
  3. Puffy face
  4. Pallor
  5. Hoarse voice
  6. Slow reflexes
  7. Dementia
  8. Goitre may be present

Investigations

  • Thyroid function tests – free T3, free T4, TSH
  • Fasting blood lipids (for elevated cholesterol level)

Treatment for hypothyroidism

Treatment objectives

The treatment objectives of hypothyroidism include the following:

  1. To correct blood level of thyroid hormones
  2. To maintain lifelong normal levels of thyroid hormones

Non-pharmacological treatment

  • Surgical intervention for pituitary lesions where necessary

Pharmacological treatment

A. Initiation of Treatment and Maintenance

Note

Start treatment with a low dose of levothyroxine, especially in the elderly and children as well as individuals with heart disease (e.g. 25-50 microgram), and adjust dose as appropriate every 6-8 weeks until TSH levels are within normal reference range.

Treatment is often life-long.
Evidence Rating: [A]
Levothyroxine, oral,
Adults: 25-200 microgram daily
Children

  • > 12 years: 25 microgram daily (max. 200 micrograms)
  • 2-12 years; 25 microgram daily (max. 100 micrograms)
  • < 2 years: 25-75 micrograms daily

Referral Criteria

Refer diagnosed or suspected cases of hypothyroidism of all ages, especially children with intellectual impairment, and individuals with pituitary disease to a specialist.