Thyroid Gland - functions
Important in tissue metabolism and development.
Secretes thyroxine (T4) plus small amount of triiodothyronine (T3).
Increases metabolism, body temperature, normal growth and development
T4 is converted to active T3 in cells and tissues by deiodinases
T3 is biologically active and influences the activity of all the cells and tissues.
Hypothyroidism features
Affects ~5% of population globally
More common in women esp elderly
Inadequate thyroid hormones during development leads to congenital hypothyroidism (cretinism) with associated irreversible brain damage.
Myxoedema coma refers to the most severe form of hypothyroidism.
Onset of the disease is usually insidious. Death is rare.
Associated w hypercholesterolaemia
Causes of hypothyroidism
Hashimoto thyroiditis (autoimmune reaction, with antibodies attacking the thyroid gland)
Hyperthyroidism treatment (Radioactive iodine, surgery)
Congenital hypothyroidism (thyroid gland not developed correctly, enzyme defects etc.)
All UK babies screened age 6-8 days old with a blood sample from a prick on the heel
Iodine deficiency still worldwide problem but uncommon
Neoplasm or Inflammation (thyroiditis)
Hypothalamus or pituitary problems
Some medicines (lithium (mood/bipolar), amiodarone (arrythmias)
Hypothyroidism symptoms?
Myxoedema (accumulation of hydrophilic mucopolysaccharides in subcutaneous tissues)
Weakness, fatigue, lethargy
Cold intolerance, decreased sweating
Dry, coarse skin, Headaches
Swelling of the face and extremities
Impaired memory and cognition, poor concentration
Mild weight gain (with anorexia)
Coarseness of voice and impaired hearing
Muscle cramps, Constipation
Diagnosis and treatment of hypothyroidism?
Measurement of thyroid stimulating hormone (TSH) levels
Low levels of T4 and T3 in the blood means -ve feedback is lost and pituitary releases more TSH
T4 (thyroxine) is also measured
Autoimmune hypothyroidism usually confirmed by the presence of thyroid specific antibodies in the blood
Treatment:LEVOTHRYOXINE (T4) is the most common.
T4 will be converted to T3 peripheral tissues. Lifelong treatment required
Thyroid hormone levels monitored yearly
What is hyperthyroidism
Excessive levels of T4 and T3.
Leading to increased metabolic rate and increased expression of beta adrenergic receptors
Women are 10 x more likely
Having other autoimmune diseases, such as type 1 diabetes or rheumatoid arthritis, increases the chances of hyperthyroidism
