What is HYPOTHYROIDISM ?

• Hypothyroidism is a state of deficient function of the thyroid gland i.e. deficient secretion of thyroid hor­mones.
• In hypothyroidism normal thyroid hormone levels are maintained by a rise in TSH. This is called subclinical hypothyroidism.
• Later free T₄ level falls and TSH levels rise further. This is the stage of clinical hypothyroidism when fea­tures of deficiency of thyroid hormones become mani­fest.
• Sub-clinical hypothyroidism is found in 10% of women over the age of 60 years.

Types of hypothyroidism

Primary hypothyroidism

• is a primary deficiency of thyroid hormones due to hyposecretion by the thy­roid gland.
• A normal TSH level means that the patient cannot have primary hypothyroidism. In primary hypothy­roidism i. e. disease of thyroid responsible for hypothy­roidism, the TSH level rises. As a screening test TSH estimation is very good.
• T₄ cannot be used as a screening test because it can­not detect sub clinical hypothyroidism (normal T₄ with elevated TSH).

Secondary hypothyroidism

•  is due to anterior pitu­itary hormone deficiencies.
• Isolated TSH deficiency is rare.
• TSH levels may be normal, low or slightly increased in secondary hypothyroidism. Free T₄ is low.

Signs and Symptoms of HYPOTHYROIDISM

• History
  • Arthralgias
  • Carpal tunnel syndrome
  • Cold intolerance
  • Constipation
  • Decreased memory, concentration
  • Decreased sweating
  • Depression
  • Hearing impairment
  • Hoarseness
  • Menorrhagia
  • Modest weight gain (10 lb [4.5 kg])
  • Muscle cramps
  • Onset may be insidious, subtle
  • Paresthesias
  • Weakness, fatigue, lethargy
• Physical Exam
  • Bradycardia
  • Coarsening or huskiness of voice
  • Delayed relaxation of deep-tendon reflexes
  • Dry, coarse skin
  • Dull facial expression
  • Hypothermia
  • Increased diastolic BP
  • Macroglossia
  • Periorbital puffiness
  • Reduced body and scalp hair
  • Reduced systolic BP
  • Swelling of hands and feet (nonpitting)

Causes of hypothyroidism:

• 1. Autoimmune hypothyroidism (Hashimoto’s thyroiditis)
• 2. Iodine deficiency
• 3. Amiodarone and lithium
• 4. Antithyroid drugs
• 5. Iodine excess
• 6. Congenital hypothyroidism
• 7. After thyroidectomy or irradiation
• 8. Thyroiditis
• 9. Hypopituitarism
• 10. Hypothalamic diseases.

Clinical Manifestations of Hypothyroidism

• · Tiredness and weakness
• · Dry skin
• · Feeling of cold
• · Hair loss
• · Difficulty in concentration and poor memory
• · Constipation, weight gain, poor appetite

HYPOTHYROIDISM Associated Conditions

• Anemia
• Depression
• DM
• Down syndrome
• Hypercholesterolemia
• Hyponatremia
• Hypoparathyroidism
• Idiopathic adrenocorticoid deficiency
• Ischemic heart disease
• Metabolic syndrome
• Mitral valve prolapse
• Myasthenia gravis
• Rapid-cycling bipolar disorder
• Vitiligo

Lab diagnosis

• · TSH estimation (elevated)
• · T₄ (Low)
• · TPO antibodies (thyroid peroxidase)
• · FNA (fine needle aspiration) biopsy
• · Elevated cholesterol and triglycerides
• · Anaemia.

Treatment of HYPOTHYROIDISM

• Levothyroxine 100 – 150 IJgjday.
• Lower doses may be given to patients of Grave’s disease who need replacement after treatment of hyperthyroidism.
• Dose is adjusted to keep the TSH levels in the lower range. TSH is measured 2 months after start of treatment.
• There is full relief after 3 – 6 months, after nor­mal TSH levels are regained.
• Levothyroxine is increased in doses of 25 IJg only. Overtreatment with T₄ (thyroxine) results in re­duced bone density and atrial fibrillation.
• Once TSH levels are stable, then TSH may be measured annually only.
• T₄ has a long half life of 7 days, therefore, any missed doses can be made up by taking 2-3 tab­lets at once.
• Pregnant women should be made euthyroid. Patients should be euthyroid before surgery. Eld­erly patients require less thyroxine.