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But recent studies show that there is another reason for TSH to be suppressed. Researches in Amsterdam have found that TSH receptor antibodies, even the blocking kind that cause hypothyroidism, may trick the pituitary. The pituitary gland is thought to also have TSH receptors. Besides getting its orders from the hypothalamus, TSH receptors in the pituitary tell it if TSH levels are adequate. Just as TSH receptors located on thyroid cells get tricked by TSH receptor antibodies, TSH receptors in the pituitary gland recognize TSH receptors antibodies as if they were TSH. Thinking there is a high concentration of TSH in the blood (when there are actually high antibody levels and no TSH), the pituitary thinks weâre hyperthyroid and quits secreting TSH.
What a nightmare for thyroid patients. Itâs no wonder that after treatment for Gravesâ disease, many patients end up complaining of hypothyroid symptoms only to be told that their labs indicate that theyâre hyperthyroid. What can be done about this? Insist that your doctor monitor you with levels of thyroid hormone, preferably levels of free T4 and free T3. Also insist on being tested for TSH receptor antibody levels.
Source: LJ Brokken, et al, âSuppression of serum TSH by GravesâIg: evidence for a functional pituitary TSH receptor,â Journal of Clinical Endocrinology and Metabolism, Oct 2001, 4814-4817.