A method is described for assessing thyroid status by estimating plasma thyroxine and dialysable thyroxine and multiplying these two to give a dialysable thyroxine index. Certain difficulties which sometimes invalidate other thyroid function tests are avoided. The techniques are relatively simple and clear differentiation between thyroid states can usually be made.

This chapter has been superceeded by 4 newer chapters, 6a, 6b, 6c, and 6d. However this Chapter, written originally by Dr Samuel Refetoff and updated by Drs Franklyn and Shephard, remains a treasure trove of information on many now-obscure thyroid tests, and references. For that reason we maintain it as a part of our Archive for use of MDs who may wish to investigate a bit of the history of thy...

The aim of the present study was to explore a possible interplay between cholinesterase inhibitors (ChEIs) and thyroid function tests (TFTs) in patients with Alzheimer's disease (AD). We reviewed thyroid function tests in 19 patients with AD before and after treatment (Rx) with ChEIs. Immunoradiometric assays were used for measuring serum thyrotropin, free thyroxin (FT4) and free triiodothyroni...

A 41-year-old woman had a 1to 2-cm asymptomatic thyroid mass, which had been monitored by an endocrinologist for several years with serial sonography. Noting that it had enlarged in the face of normal thyroid function tests, the endocrinologist ordered a fine-needle aspiration biopsy, which showed a cellular follicular lesion. Although some of the nuclear changes seen in papillary carcinoma wer...

This issue of Clinical Chemistry contains 3 reports from the IFCC Working Group for Standardization of Thyroid Function Tests. The first report relates to thyroidstimulating hormone (TSH) (1 ), the second addresses free thyroxine (FT4) and free triiodothyronine (FT3) (2 ), and the third discusses total thyroxine (T4) and total triiodothyronine (T3) (3 ). Each of these reports is authored by a g...

Laboratory tests are essential for accurate diagnosis and cost-effective management of thyroid disorders. When the clinical suspicion is strong, hormonal levels just confirms the diagnosis. However, in most patients, symptoms are subtle and unspecific, so that only biochemical tests can detect the disorder. The objective of this article is to do a critical analysis of the appropriate use of the...

Changes in plasma thyroxine (T4), triiodothyronine (T3), free thyroxine index (FT4I) and thyroid stimulating hormone were studied in 100 patients with Graves' disease treated with carbimazole. During therapy plasma T3 concentrations were disproportionately high compared to those of T4, the T4 : T3 ratio was low, and many patients were clinically euthyroid with a normal plasma T3 but low T4 conc...