The season in which a common thyroid test (TSH)  is performed may be important in the decision to treat thyroid conditions.Subclinical hypothyroidism is frequently reversible. In cases with minimal TSH elevation, it is prudent to perform follow-up tests in the summer-fall season before deciding on treatment, particularly in the areas with a wide annual temperature range.

Since thyroid hormone plays a role in body temperature regulation, it makes sense that colder climates may be associated with higher levels  Physicians may have to check the hormone levels in different seasons to decide if treatment is needed.

If you are concerned about hormonal problems,  check with your physician.  Also,  you can get tests ordered via online services through Quest Diagnostics.