The thyroid gland produces hormones that regulate metabolism, energy production, temperature regulation, and much more. When it is underperforming — a condition called hypothyroidism — the effects are wide-ranging and often misattributed to other causes.

Here are five signs worth discussing with a clinician.

1. Persistent Fatigue That Does Not Improve With Rest

This is the most common complaint we hear from patients who are eventually diagnosed with thyroid dysfunction. It is not ordinary tiredness — it is a heaviness that sleep does not resolve.

2. Unexplained Weight Gain or Difficulty Losing Weight

When metabolism slows due to insufficient thyroid hormone, weight gain can occur even without changes in diet or activity. Weight loss becomes disproportionately difficult.

3. Cold Sensitivity

Feeling consistently colder than others in the same environment — particularly in the hands and feet — is a classic presentation of low thyroid function.

4. Hair Thinning or Loss

Thyroid hormones play a critical role in hair follicle cycling. Both hypothyroidism and hyperthyroidism can cause diffuse hair thinning, including loss from the outer third of the eyebrows.

5. Brain Fog and Memory Issues

Difficulty concentrating, slow thinking, and memory lapses are neurological manifestations of thyroid insufficiency that are frequently attributed to stress or aging.

The Importance of Comprehensive Testing

A TSH alone is not sufficient to evaluate thyroid function. We assess TSH, free T3, free T4, and thyroid antibodies. Optimal ranges differ from laboratory reference ranges, and we interpret results in the context of symptoms — not numbers alone.