Lab test shows normal T3 ,T4 and TSH levels but signs of hyperthyroid are present like hair shedding, increase Heart rate, irritability. Is it possible to be hyperthyroid or can there be other disease.Hyperthyroid is in remission from last 10 months. Endocrinologist said levels are fine.
The personal set-point of thyroid homeostasis may differ between individuals [1, 2]. Multiple studies showed that the intra-individual variation of both TSH and peripheral thyroid hormones is smaller than the inter-individual variation [3, 4]. Therefore, for individuals the range of optimality is smaller than the width of the corresponding reference range (for TSH, free T4 and potentially free T3, too) . A person with a rather low setpoint may well have symptoms of thyrotoxicosis like irregular heart rhythm, increased heart rate etc. if the FT4 concentration is higher than her or his personal set point.
The potentially harmful consequences of this association were dramatically demonstrated by the Rotterdam study, which showed a fourfold-increased risk of sudden cardiac death in persons with FT4 concentration being in the highest tertile of the normal reference range . A similar association was found to atrial fibrillation . Recently, the THORACAL study found an increased risk of severe cardiac arrhythmia in persons with higher FT4 concentration (of note within the reference range again) .
Of course, there may be other reasons for increased heart rate, hair loss etc. as well. But it may be beneficial to check the thyroid, e.g. via ultrasound or antibody determination. It is not advisable to take thyrostatic agents without a definitive diagnosis of hyperthyroidism, however.
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Chaker L, Heeringa J, Dehghan A, et al. Normal Thyroid Function and the Risk of Atrial Fibrillation: the Rotterdam Study. J Clin Endocrinol Metab. 2015;100(10):3718–3724. doi:10.1210/jc.2015-2480 https://pubmed.ncbi.nlm.nih.gov/26262438 https://doi.org/10.1210/jc.2015-2480
Patrick Müller, Johannes W. Dietrich, Tina Lin, Alexandru Bejinariu, Stephan Binnebößel, Friederike Bergen, Jan Schmidt, Sarah-Kristin Müller, Apostolos Chatzitomaris, Muhammed Kurt, Shqipe Gerguri, Lukas Clasen, Harald H. Klein, Malte Kelm, Hisaki Makimoto, Usefulness of Serum Free Thyroxine Concentration to Predict Ventricular Arrhythmia Risk in Euthyroid Patients with Structural Heart Disease. The American Journal of Cardiology, 2020. https://www.sciencedirect.com/science/article/abs/pii/S0002914920300606 https://doi.org/10.1016/j.amjcard.2020.01.019