Thyroid MDS Dr Mojiminiyi

5th Year Thyroid MDS Segun Mojiminiyi 2005 What is your INITIAL Diagnosis? Diagnosis of Hyperthyroidism HYPERTHYROIDISM Diagnosis : • Largely clinical..... • Role of the Laboratory……? The Role of Clinical Chemistry  (a) screening  (b) Confirm INITIAL diagnosis  (c) determination of the cause  (d) monitoring of treatment  (e) Detection of recurrence Investigation of Thyroid Disease more TSH = more T3/4 more T3/4 = less TSH So what investigations were requested in the patients presented? Assessment of Thyroid Function Basic Tests • Free Hormones FT4, FT3 • TSH • Othet tests? Thyroid Stimulating Immunoglobulins Laboratory Findings in Hyperthyroidism Test • T4 • T3 • FT4 • FT3 • TSH • Others: Expected Result – Anti-TSH receptor autoantibodies +++ ("thyroid stimulating antibody", "long-acting thyroid stimulator"=LATS), - anti-thyroglobulin antibodies +++ Sometimes Things are not so clear……. Condition T3 Toxicosis TSH Suppressed fT4 N fT3 H Sub-clinical Thyrotoxicosis Suppressed N N Other Thyrotoxic States… Laboratory Findings in Thyrotoxicosis Factitia Test • T4 • T3 • FT4 • FT3 • TSH • Thyroglobulin Expected Result TSH producing pituitary adenoma • Pituitary adenoma that secretes TSH (extremely rare). Test Expected Result • • • TSH FT4 FT3 Amiodarone inhibits peripheral deiodination of thyroxine to triiodothyronine • • • • • • TT4 FT4 rT3 (reverse T3) TT3 FT3 TSH      small  or • Could cause clinical hypothyroidism hyperthyroidism. • The incidence is 2% for each condition. Thyroid Hormone Resistance Extremely rare • Could be: –Generalised or –Confined to the pituitary Generalised resistance • • • TSH FT4 FT3    • Patient could be clinically hypothyroid, euthyroid or even hyperthyroid Pituitary resistance • TSH  • FT4  • FT3  • Since the peripheral tissues are not resistant to thyroid hormones, these patients are hyperthyroid Monitoring Treatment of Thyrotoxicosis • Measure Serum TSH, FT4, FT3 • TSH suppression may persist for months • Long-term drug treatment: –serum TSH gives a reliable index of therapy.