What is the cause for TSH fluctuations?
Q: In viral thyroiditis, what is the cause of TSH fluctuations from hyper- to hypo-thyroidism? Should treatment be started during this period of fluctuations or is it recommended to wait until the levels reach a baseline or stabilise? Do these laboratory results stabilise or return to normal limits in time? If so, how long does it typically take? Also, the antibodies are highly elevated - do these levels fluctuate as well? Do these laboratory results stabilise or return to normal limits in time? If so, how long does it typically take?
A:Let me start with the difference between thyrotoxicosis and hyperthyroidism. Thyrotoxicosis is a broad term used for any patient having excessive thyroid hormones due to any cause including over treatment with L-Thyroxin in patients with hypothyroidism. In hyperthyroidism the cause is increased production of thyroid hormones from the thyroid gland meaning the gland is hyperfunctioning. In thyroiditis there is release of preformed thyroid hormones from the gland. These two conditions can be differentiated using radioiodine uptake studies. In thyroiditis, uptake will be low and hyperthyroidism uptake will be high. In thyroiditis, initially patients have low TSH and subsequently the thyroid hormone can either become normal or patient can go into hypothyroidism. One should not give specific treatment during initial phase of 8-12 weeks; by that time it becomes clear whether patient will remain hypo or normal. High anti-TPO means auto immunity and if hypothyroid, these patients need medication lifelong. Fluctuations in anti-TPO positive patients is usually due to treatment with thyroxine and if properly treated should settle down.