A Ganie, S Kalra
A Ganie, S Kalra. Hypothyroidism: Clinical Features . The Internet Journal of Family Practice. 2009 Volume 8 Number 2.
Hypothyroidism is a clinical syndrome resulting from deficiency of thyroid hormones in the target tissues, leading to generalized slowing of all metabolic processes. Hypothyroidism in infants and children results in marked slowing of growth and mental development, which may be irreversible if not corrected early. In adults, most of the components of the syndrome is reversible.
Primary hypothyroidism is common worldwide especially in iodine deficient areas like India. In non-endemic areas chronic autoimmune thyroidectomy (incidence 3.5/1000 women/ year and destructive treatment of thyrotoxicosis (6.6/1000 women per year) are commoner. Epidemiologic studies like Wickham county study show high prevalence (18/1000) of subclinical hypothyroidism, female preponderance and increasing incidence with age
Depends upon the age of the patient
Energy and Metabolism
BMR and O2 consumption is reduced leading to hypothermia and increase in body weight. Glucose tolerance curve becomes flatter and protein metabolism is decreased. The latter affects growth and development in children. Cholesterol rises primarily because of LDL rise due to low expression of LDL receptors.
Skin and appendages
Skin is dry, pale, thick, rough and cold because of decreased function of sebaceous and sweat glands. Carotene deposition can lead to yellowish discoloration. There is hair loss at many places and nails may become brittle. The mucopolysaccharide deposition leads to non pitting edema.
In adults CNS has low voltage EGG, prolonged conduction time and reduced visual evoked response (VER) and somatosensory evoked response (SSER) resulting in hyper somnolence and mental slowing. Depression is common (40%) and rarely agitation and anxiety can occur (myxedema madness). Cerebellar ataxia, carpel tunnel syndrome, various other polyneuropathies may occur.
Myalgia, stiffness, crumpts and weakness are common. Type II white fast fibrin change to type I slow ones. The tendon jerks have delayed relaxation. Joint stiffness and arthralgia are common. Bone turnover as indicated by markers is low.
Dynamics indicates increase in peripheral vascular resistance (50-60%) and decrease (30-50%) in cardiac output. Mild diastolic hypertension may occur this. Symptoms and signs are dypsnea, effort, intolerance, bradycardia, weak heart sounds and cardiomegaly (pericardial effusion or cardiomyopathy).
Dyspnoea, and sleep apnea can be due to muscle weakness, respiratory centre depression, pulmonary dysfunction. Reduced drive (34%) may lead to hypoxia and hypercarbia.
GFR and free water clearance is decreased in view of altered cardiovascular hemodynamics. Hyponatremia can occur due to low free water clearance and increased AVP levels. Serum creatinine may rise by 10-20%.
Sexual maturation is delayed (rarely precocious puberty due to spill over activity of TRH and TSH) in children.Adult men can have decreased libido and potency but normal semen analysis and normal gonadal axis. In females, ovulatory surge may be affected leading to menorrhagia with anovulatory cycles. Amenorrhoea galactorrhoea syndrome can occur because of elevated prolactin.
Accuracy of 12 symptoms and signs in the diagnosis of primary hypothyroidism
The medical history reveals gradual onset progressive lethargy, history of thyroid disease (surgery or radioablation). Clinically patient is hypothermic (Temp <75°F), gross features of myxedema and may have signs of precipitating illness. Among precipitating factors infections are most important commonest being respiratory and urinary tract. Other precipitating factors are sedative, sedative drugs, cardiovascular events or cerebrovascular events. Patients may have hypoglycemia, hyponatremia, hypoxia with hypercarbia which can contribute to the comatose state. ECG may show bradycardia with low voltage. Hypothermia may be missed by ordinary thermometer and hence standard lab type thermometer should be used. Mild diastolic hypertension or normal blood pressure may be erroneous due to cutaneous vasoconstriction, and thus rapid warming may lead to severe hypotension.
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