Chemistry, toxicology & urinalysis
Organ specific
Thyroid
Hyperthyroidism-lab diagnosis
Author: Nat Pernick, M.D.
Last author update: 1 March 2011
Last staff update: 29 September 2021
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Hyperthyroidism [title] chemistry
Table of Contents
Definition / general | Etiology | Diagnosis | Laboratory | Treatment | Additional referencesCite this page: Pernick N. Hyperthyroidism-lab diagnosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/chemistryhyperthyroidism.html. Accessed December 21st, 2024.
Definition / general
- See also Hyperthyroidism in Thyroid chapter
- Hyperfunction of gland (usually elevated levels of free T3 / T4, but see subclinical hyperthyroidism below)
- Thyrotoxicosis refers to clinical effects of free thyroid hormone
- Source may not be thyroid gland
- May be masked by nonthyroidal illness syndrome (J R Soc Med 2003;96:185)
Etiology
- Graves disease (85%-circulating autoantibodies to TSH receptor)
- Overdose of exogenous thyroid hormone, hyperfunctioning multinodular goiter or thyroid adenoma, thyroiditis, struma ovarii, iodide ingestion, choriocarcinoma/hydatidiform mole, maternal Graves disease, pituitary adenoma
Diagnosis
- High free T4
- TSH may be low (primary hyperthyroidism) or high (secondary hyperthyroidism)
- In subclinical hyperthyroidism, T3 and T4 are normal but TSH is low
Laboratory
Primary hyperthyroidism
Secondary hyperthyroidism
Subclinical hyperthyroidism
T3 hyperthyroidism
T4 hyperthyroidism
- Intrinsic thyroid gland abnormality producing excess T4
- High free T4, low TSH, normal TRH stimulation test
Secondary hyperthyroidism
- Abnormal TRH stimulation test (problem is at level of pituitary, including TSH producing tumors), high TSH, high free T4
Subclinical hyperthyroidism
- Low TSH (< 0.1 μIU/ml), normal T3 and T4 (Eur J Endocrinol 2005;152:1), no clinical hyperthyroidism
- May be due to exogenous thyroid (Hormones (Athens) 2006;5:119)
- Patients have increased risk of atrial fibrillation, cardiac death and osteoporosis
T3 hyperthyroidism
- 1 - 4% of hyperthyroid patients
- Low TSH, high free T3, normal free T4
- Associated with early treatment of hyperthyroidism with antithyroid drugs
T4 hyperthyroidism
- High T4, normal T3
- Due to primary hyperthyroidism causes, also iodine, amiodarone (Arch Pathol Lab Med 2003;127:e275), pregnancy (2%)
Treatment
- Beta blockers for symptoms, thionamide-type drugs to block new hormone synthesis, iodine to block release of T4/T3
Additional references
