Hypothyroidism, Causes, Diagnosis and Laboratory Evaluation, Signs and Symptoms, Management

Hypothyroidism


Hypothyroidism results from under section of the thyroid gland


Hypothyroidism is classified as follows 

Primary hypothyroidism: Failure of thyroid gland 

Secondary hypothyroidism: Due to pituitary failure 

Tertiary hypothyroidism: Due to hypothalamic failure 

Causes of Hypothyroidism

Worldwide, hypothyroidism resulting from iodine deficiency remains an all too common problem 

In non-endemic areas or Iodine sufficient areas, Hishimoto thyroiditis, a choronic autoimmune disease, is the most common cause of primary hypothyroidism 

Other causes are 
  • Surgical removal of the thyroid gland 
  • Thyroid gland ablation with radioactive iodine 
  • A biosynthetic defect in iodine organification 
  • Replacement of the thyroid gland by tumor 
  • Drugs such as lithium or interferon 
  • Pituitary and hypothalamic disease 

Hashimoto's Thyroiditis

Hashimoto's thyroiditis is chronic autoimmune thyroiditis which is characterized by high levels of circulating antibodies directs against
  • Thyroid peroxidase (TPOAb) 
  • Thyroglobulin (TgAb)
  • TSH receptor (TSH-R Ab)
Thereby, exacerbating the hypothyroidism. 

Diagnosis and Laboratory Evaluation

The most valuable test is a sensitive measurement of TSH. 

Additional test may include the following
  • Free T4 estimate 
  • Thyroid autoantibodies-antithyroid peroxidase and antithyroglobulin autoantibodies.
  • Thyroid scan, ultrasonography, or both(to evaluate structure thyroid abnormalities) 

Signs and Symptoms of Hypothyroidism

Symptoms 

  • Tiredness, weakness
  • Dry skin 
  • Feeling cold 
  • Hair loss 
  • Difficulty concentrating and poor memory 
  • Constipation
  • Weight gain with poor appetite 
  • Dyspnea 
  • Hoarse voice 
  • Menorrhagia
  • Paresthesia 

Signs 

  • Dry coarse skin 
  • Cool peripheral extremities 
  • Puffy face, hands, and feet 
  • Bradycardia
  • Peripheral edema 

Overt and Sub-Clinical Hypothyroidism 

Overt Hypothyroidism
  • High levels of TSH 
  • Low levels of free T4 and T3 with 
  • More apparent symptoms 
Sub Clinical Hypothyroidism
  • Mildly increased TSH levels 
  • Normal free T4 and T3 levels with 
  • Few or no symptoms 
Although subclinical hypothyroidism is often asymptomatic, potential risks includes
  • Progression to overt Hypothyroidism
  • Cardiovascular effects 
  • Hyperlipidemia
  • Neuropsychiatric effects. 

Management of Hypothyroidism 

Thyroxine (Levothyroxine sodium) is the hormone of choice for hypothyroidism due to its consistent potency and prolonged duration of action 

Levothyroxine therapy relies on deiodinases to convert T4 to T3 to maintain a steady level of free T3 

The goal of therapy is to normalise the serum TSH (in primary hypothyroidism) or free T4 ( in secondary or tertiary hypothyroidism ) and to relieve symptoms of hypothyroidism. 




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