A direct relationship exists between the amount of TSH in the sample and the RLUs detected by the instrument optical system.

Detection technology Label Separation step Solid phaseTechno-logy Fluorscence detector Alkaline phosphatase enzyme Glass fiber matrix Latex microparticle MEIA Chemiluninescence photomultiplier tube Chemiluminescent compound magnet Magnetic micriparticle CMIA

There are two types of reaction sequences or formats for MEIA assays: – One step: Sample, microparticles and conjugate are combined in the incubation well of the reaction vessel. – Two step: Sample and microparticles are combined in the incubation well of the reaction vessel and the conjugate reaction takes place on the matrix cell.

1.Radioactive iodine tests, testing uptake by the thyroid gland 2.Hormones concentration T3,T4 3.Thyroid Binding Globulin 4.Concentration of TSH 5.Urinary excretion of thyroid hormones 6.Tests influenced by the actions of thyroid hormones.(glucose tolerance test, calcium, cholestrol) 7.Thyroid antibody tests for cases autoimmune.

The main contribution of chemical measurements to the investigation of thyroid disease is to help sub-divide patients into the categories of effects of treatment.

FT3 - FT3 has little specificity or sensitivity for diagnosing hypothyroidism and adds little diagnostic information. The main value of FT3 is in the evaluation of the 2 to 5% of patients who are clinically hyperthyroid, but have normal FT4. In this situation, an elevated FT3 would be suggestive of T3 toxicosis, in which the thyroid secretes increased amount of T3 or there is excessive conversion of T4 to T3.

The interpretation of results for serum T4 needs to take into account alterations in the thyroid-binding proteins. The free thyroxine index (FTI) is determined by the following calculation:  FTI = Thyroxine (T4)/Thyroid Binding Capacity  The FTI is a normalized determination that remains relatively constant in healthy individuals and compensates for abnormal levels of binding proteins.  Hyperthyroidism causes increased FTI and hypothyroidism causes decreased value.

FT4: This test measures the metabolically active, unbound portion of T4. Measurement of FT4 eliminates the majority of protein binding errors associated with measurement of the outdated total T4, in particular the effects of oestrogen.

There are marked variations in the thyroid function with age, evident in all of the vitro hormone and proteins measurements. In general thyroid function parameters in healthy subjects show little or no clinical significant gender or racial variation.

Quality control, the best step for all analytical tests to have a reliable result and a voiding the errors. Pre analytical Analytical process Post analytical process

A 63-year-old woman has Hashimoto’s disease. Her thyroid laboratory values today include the following: She feels consistently run down and has dry skin that does not respond to the use of hand creams. The hormones levels: TSH 10.6 mIU/L (normal (0.5–4.5 mIU/L) A free T4 concentration of 0.5 ng/dL (normal 0.8–1.9 ng/dL).