Algroithm of Thyroid Function

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High TSH & Low FT4 - Primary hypothyroidism, drug induced hypothyroidism and Hashimoto's thyroiditis

High TSH Normal FT4 - Subclinical hypothyroidism, intermittent T4 therapy, REcovery phase of nonthyroid illness

High TSH & High FT4 - TSH secretign pituitary adenoma, thyroid hormone resistance, poorly compliant hypothyroid patients who take levothyrozine sporadically

Normal TSH & Low FT4 - Central hypothyroidism, nonthyroidal illness, Hashimoto's thyroiditis

Normal TSH & Normal FT4 - Euthyroid

Normal TSH & High FT4 - TSH secreting pituitary adenoma, thyroid hormone resistance

Low TSH & Low FT4, Low TT3 - Central hypothyroidism, non thyroidal illness, hyperthyroidism patients recieving excessive levothyrine therapy

Low TSH & Normal FT4, Normal TT3 - Subclinical hyperthyroidism, medications: corticosteroids, dopamine, dobutamine

Low TSH & High TT4, High TT3 - Hyperthroidism of any type, Grave's disease, Toxic mulinodular goiter, Toxic adenoma, Gestational transiet throtoxicosis, thyroiditis, factitous thyrotoxicosis, drug induced hyperthyroidism

TSH - thyroid stimulating hormone

FT4 - Free thyroxine

TT3 - total triiodothyronine