Presentation on theme: "Hypothyroidism Dr Fidelma Dunne Senior Lecturer Department of Medicine UCHG."— Presentation transcript:
Hypothyroidism Dr Fidelma Dunne Senior Lecturer Department of Medicine UCHG
Synthesis and Secretion Follicular cells arranged in clumps. Clumps of cells contain colloid. Colloid an iodine containing protein called thryoglobulin. This is the precursor and storage form of thyroid hormone. Thyroxine (T4), Triiodothyronone (T3)
Thyroid hormone action T4 and T3 circulate in the blood bound to plasma proteins. TBG(70%), TBPA(20%) and albumin(10%). T3 is the active form, 5 times more active than T4. T4 is converted to T3 outside the thyroid, mostly in liver and kidney. T3 binds to a nuclear receptor
Regulation of the H-P-T axis TRH secreted from hypothalmus controls TSH production. TSH from anterior pituitary stimulates secretion of T4 and T3 from thyroid. Regulated by a negative feedback loop.
Prevalence of Hypothyroidism Prevalence is 14/1000 females and 1/1000 males. Other autoimmune diseases. Family history of autoimmune diseases
Clinical features General and CVS Tiredness Weight gain Cold intolerance Goitre Constipation Bradycardia Angina Cardiac Failure Pericardial effusion
Clinical Features Neurological and Haematological Aches and Pains Carpal Tunnel Deafness Hoarseness Ataxia Depression Psychosis Iron deficiency A Pernicious Anemia
Clinical Features Skin and Reproduction Dry skin Erythema ab igne Vitiligo Infertility Menorrhagia Galactorrhoea
Laboratory Diagnosis T4/FT4 reduced T3/FT3 TSH elevated Thyroid Antibodies may indicate aetiology. If TSH is reduced or normal in the presence of a low T4, pituitary function necessary.
Additional abnormal tests. Fasting cholesterol and triglycerides may be raised Ck AST and LDH (SMAC 20) may be raised FBC Anemia ECG Slow rate. Small complexes.
Treatment Thyroxine. Usual maintenance dose is 150ug. Compliance and adequacy of dose checked by TSH measurements. Try to maintain TSH in normal range.
Subclinical Hypothyroidism Primary thyroidal failure (Hashimotos) is a gradual process. Non specific symptoms Reduced thyroid activity has been compensated by an increase TSH output to maintain a euthyroid state. Normal T4/FT4 with elevated TSH. Thyroid antibodies usually positive
Treatment Repeat tests after an interval. If TSH is continuing to rise in the presence of strongly positive antibodies, the risk of developing hypothyroidism in the future is high. Thus treatment with thyroxine at this early stage may be justified if symptomatic. Beware-Thyroxine may not cure all symptoms.
Myxoedema Coma Requires prompt treatment. Mortality of 50%. Suspect in cases of hypothermia. T3 20ug bd IM Steroids recommended Glucose to correct hypoglycaemia Rewarming Assisted ventilation
Thyroid hormone deficiency in Pregnancy Goitre is common in pregnant women (70%). TBG increased, thus total T4 and T3 increased. FT4 and FT3 are normal and TSH remains unchanged. Hypothyroidism treated with thyroxine during pregnancy. Dose requirements increase. A change in dose usually needed each trimester.
Post-partum thyroiditis. Incidence is about 9%. Transitory or permanent. Early hyperthyroidism ( 4/12), euthyroid 10/12 later. Increased microsomal antibodies. Thyroxine
Elderly Non specific symptoms Osteoporosis Anemia Heart Failure Treatment with thyroxine Start with small doses and titrate slowly. (25ug).
TFTs in severely ill patients Sick euthyroid syndrome A low serum T4 due to abnormality of binding to serum proteins. A low serum T3 due to reduced production. TSH normal Clinically euthyroid.
Summary Suspicion Women Previous thyroid disease or treatment Other autoimmune diseases. Elderly- caution with treatment