As difficult as it may be to decipher the symptoms of improper thyroid function, stress and adrenal fatigue may also be part of the problem. Acute stress results in high cortisol levels, which interferes with the conversion of T4 to active T3. Stress does this, in part, by inhibiting the absorption of selenium and other nutrients like vitamins A, B6, and B12, which are vital to proper T4 conversion. Ironically, low cortisol levels (which result from adrenal fatigue due to chronic stress) also impair thyroid function by interfering with T3’s ability to enter the cells. Without making sure the adrenals are functioning properly or understanding how stress affects thyroid function, a vicious cycle continues, even with traditional thyroid supplementation. Oral hydrocortisone is available as Cortef and in compounded preparations.