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Hypothyroidism

Definition
A disease condition  resulting from suboptimal levels of thyroid hormone.
Thyroid deficiency can affect all body functions
Mild form, subclinical forms, myxedema

Aetiology
Most common cause in adults : autoimmune thyroiditis (Hashimotos disease)
Hashimoto's disease - initially hyperthyroidism followed by hypothyroid status
Hypothyroidism treated with  radio iodine or antithyroid medications
Post operative
Radiation therapy for head and neck cancer
Other causes is listed in the chart

Pathophysiology
More than 95% have primary  or thyroidal hypothyroidism - i.e. dysfunction of the thyroid gland itself
When it is due to  failure  of the pituitary gland, hypothalamus or both it is known as central hypothyroidism or secondary hypothyroidism
Congenital hypothyroidism - Cretinism. The mother may have hypothyroidism
Myxedema : accumulation of mucopolysaccharides in subcutaneous and other interstitial tissues - occurs in long standing hypothyroidism

Clinical Manifestations
Between 30 and 60 yrs
Women affected five times more than men
May be associated with goitre
Congenital hypothyroidism is called cretinism
Extreme fatigue
Hair loss
Brittle nails
Dry skin, thickened
Numbness and tingling of the fingers
Husky voice - hoarseness
Menstrual disturbances -  menorrhagia/amenorrhea
Loss of libido
Subnormal temperature and pulse rate
Weight gain without increased food intake
Cachexia may also occur
Face becomes expressionless and mask like
Feeling cold even in a warm environment
Emotional responses subdued
Mental process dulled, patient apathetic
Slow speech
Tongue enlarges
Hands and feet  increase in size
Constipation
Deafness
Advanced hypothyroidism Personality and cognitive changes dementia
Inadequate ventilation and sleep apnea
Pleural effusion, Pericardial effusion, respiratory muscle weakness
Elevated serum cholesterol, atherosclerosis, IHD, poor left ventricular function  in severe hypothyroidism
Hypothermia
Abnormal sensitivity to sedatives, opioids and anesthetic agents
Patients with unrecognized hypothyroidism undergoing surgery are at increased risk for intraoperative hypotension and postoperative heart failure and altered mental status
Myxedema coma - extreme hypothyroidism
Respiratory drive is depressed alveolar hypoventilation, progressive CO2 retention, narcosis and coma
Cardiovascular collapse and shock may require aggressive and intensive therapy : mortality is high

Alterations in immune function with aging calls for regular screening of TSH levels in the elderly of 60 or more age

Medical Management
Pharmacologic therapy
Synthetic levothyroxine (Eltroxine)
Dosage depending on TSH; TSH under 10mIU/l do not require treatment unless they have symptoms of hypothyroidism
May start with 25 µg and go on raising every month or every two  months titrating with TSH Levels. Total replacement dose is 400 µg / day.
Prevention of Cardiac Dysfunction
When eltroxine started sudden increase in O2 requirement of the heart may cause ischaemia - should be done very cautiously with a physician's  supervision
Prevention of hypothyroidism
Salt iodization
















































insert pic :  A 3-month-old infant with untreated congenital hypothyroidism showing myxedematous facies, a big tongue, and skin mottling