The adrenal glands release stress hormones, cortisol and adrenaline in response to a stressor. If the stress continues for a long period of time, the adrenals can no longer meet the demands for putting out a continuous supply of stress hormones leaving the adrenals and you exhausted. What happens next is that this high level of adrenal stress hormones disrupt the normal functions of the thyroid gland which is why the adrenals need to be addressed prior to the thyroid.