Purpose Poor sleep and the accompanying TSH (Thyroid Stimulating Hormone) elevation are not uncommon since TSH secretion is controlled by the circadian rhythm. However, the true relationship between poor sleep and TSH elevation is unclear, and hence we aimed to elucidate this association by cross-sectional and longitudinal studies. Methods Participants with isolated elevated and normal TSH concentration were recruited, and the Pittsburgh Sleep Quality Index (PQSI) was used to assess sleep

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... . The patients with isolated TSH elevation were followed up longitudinally, and TSH levels were remeasured when sleep status improved. Results The proportion of poor sleep and occasional poor sleep among subjects with isolated TSH elevation was significantly higher than that in subjects with normal TSH (70.24% vs. 49.58%, p = 0.001; 9.52% vs. 1.68%, p = 0.006), and the ratio of good sleep was obviously decreased in subjects with isolated TSH elevation than normal TSH (20.24% vs. 48.74%, p < 0.001). Patients with isolated TSH elevation had significantly higher PSQI scores in the subjective sleep quality, sleep latency, sleep duration, and habitual sleep efficiency dimensions than subjects with normal TSH (all p < 0.05). In the follow-up study, among patients with isolated TSH elevation at baseline, the ratio of TSH normalization in patients who slept better was significantly higher than that in patients who still slept poorly (85.42% vs. 6.45%, p < 0.001). Conclusion This study revealed isolated elevated TSH concentrations tends to normalize when sleep status improves, and we recommend that clinicians inquire about sleep status thoroughly and reexamine thyroid hormone levels when sleep status improves.