Hypothyroidism biochemical diagnosis

Clinical manifestations of overt hypothyroidism are usually obvious though minor deficiencies may be more easily missed they may have pronounced adverse effects on patients well-being. The diagnosis nowadays should always be confirmed biochemically (with detection of low serum T4 and high TSH levels), and highly sensitive and specific immunoassays are now readily available in most countries. 

Results in Hyperthyroidism. Patients with hyperthyroidism fail to respond to TRH because of the elevated circulating levels of T3 and T4. The main diagnostic application of the TRH test is in the exclusion of mild or subclinical hyperthyroidism, since a normal response absolutely excludes this diagnosis. However, an impaired or absent response to TRH is not in itself pathognomonic of hyperthyroidism since it can be seen in patients with ophthalamic Graves disease (01), autonomous thyroid adenomata (El), supraphysiological replacement with T4 or T3 for hypothyroidism and in some subjects rendered clinically and biochemically euthyroid after treatment of hyperthyroidism (V4). This transient lag in restoration of normal TSH response to TRH makes the... 

Old data on iodine intake were sometimes incomplete or even questionable. For instance, in most cases, there was no clear concept of environmental factors such as goiter-causing agents (e.g. thiocyanate or flavonoids). Even more, the clinical examination has low sensitivity and specificity for the diagnosis of hypothyroidism. Indeed, examination of large cohorts of subjects in Zaire revealed that one out of two subjects, clinically classified as euthyroid, had clear biochemical evidence (low serum T4 and/or high serum TSH) characteristic of hypothyroidism. ... 

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