Factors that can affect serum thyroid-stimulating hormone (TSH) levels
| Factor | Explanation |
|---|---|
| Time of day | TSH levels naturally fluctuate throughout the day, peaking in the early morning hours |
| Season of year | TSH levels may be slightly higher in winter than in summer, potentially due to changes in sunlight exposure or other environmental factors |
| Stress | Can temporarily suppress TSH production |
| Illness | Infections or autoimmune diseases can disrupt the hypothalamic-pituitary-thyroid axis, leading to changes in TSH levels, depending on the severity or duration of the illness |
| Medications | Some medications, particularly those used to treat thyroid disorders or other conditions, can influence TSH levels |
| Interindividual variation | There can be significant individual differences in TSH patterns, even among healthy individuals; genetic factors and personal characteristics may play a role |
| Age | TSH levels tend to increase with age, particularly in older adults |
| Sex | Some studies suggest that there may be sex-specific differences in TSH regulation, so that women tend to have higher TSH levels than men14 |
| Autoimmunity | Autoimmune thyroid diseases such as Hashimoto thyroiditis can lead to elevated TSH levels, particularly in the early stages of the disease |
Based on information from references 14–21.