Thyroid hormone resistance

The most common cause of the syndrome are hereditary mutations of the Thyroid Receptor B, of which over 100 different mutations have been documented.

Thyroid hormone resistance syndrome is extremely rare, incidence is variously quotes as 1 in 50,000 or 1 in 40,000 live births.

The syndrome can present with various symptoms depending on the nature of the mutation, typically some or all tissues are resistant to taking up thyroid hormone, so despite raised measures of serum thyroid hormone the individual may appear euthyroid. It has also been linked to some cases of Attention deficit hyperactivity disorder (ADHD).

The characteristic blood test results for this disorder are more likely explained by other disorders (for example pituitary adenoma, or other pituitary disorders), as such diagnosis may involved identifying a mutation of the thyroid receptor to eliminate other possible causes.

Sometimes the phrase 'thyroid hormone resistance' is incorrectly used to identify cases where patients with autoimmune thyroid disorders respond poorly to normal doses of replacement thyroid hormone, this is thought to occur where patients have antibodies to thyroid hormones. Antibodies to thyroid hormones quite commonly occur in such disorders, and may interfere with the normal clinical assays used in monitoring such disorders, and in unusual cases may have further independent clinical significance.