How to identify subclinical hyperthyroidism

Subclinical hyperthyroidism can be caused by multiple things. In this video from our Thyroid Disease Masterclass, we'll cover the lab patterns consistent with subclinical hyperthyroidism, describe the possible etiologies, and identify what could go wrong if this condition is left untreated.

Master the management of thyroid disease. In our Thyroid Disease Masterclass, Dr Tracy Tylee–Clinical Assistant Professor of Endocrinology at the University of Washington–will review the pathophysiology of thyroid dysfunction, discuss the interpretation of thyroid tests, explain how pregnancy and certain medications can alter thyroid function, and evaluate the best treatment options.

[00:00:00] Patients will sometimes have a suppressed TSH with normal thyroid hormone levels. This is a condition known as subclinical hyperthyroidism. This can be due to illness, toxic nodules, Grave's disease, resolving thyroiditis or normal response in early pregnancy. For patients with small, hyperfunctioning thyroid nodules, these release excess thyroid hormone, which acts at the thyroid to decrease the TSH. The low TSH

[00:00:30] can actually inhibit thyroid hormone production in the remaining thyroid gland and so thyroid hormone levels can remain normal. For patients with early Grave's disease, the antibody binds to the TSH receptor, which stimulates thyroid hormone production in the thyroid and release of that thyroid hormone into the circulation. This acts with the pituitary to decrease the TSH, which in early Grave's disease is able to regulate thyroid hormone production and maintain thyroid hormone levels in the normal range, despite the increased stimulation

[00:01:00] by the antibodies. For patients with resolving thyroiditis, subclinical hyperthyroidism is seen once the thyroid hormone levels start returning to normal but the TSH is lagging behind. So, if labs are checked during this time period, thyroid hormone levels will appear normal but the TSH has not yet recovered. Clinical complications associated with subclinical hyperthyroidism include decreased bone mineral density and increased risk of arrhythmias and possible increased risk of cardiovascular deaths.

[00:01:30] Given these clinical features, we typically treat patients who would be most at risk from these complications including elderly patients, patients with a history of cardiovascular disease and patients with low bone mineral density.