Protirelin (thyrotropin-releasing hormone) in thyroid gland: possible involvement in regulation of thyroid status.

Aim: To establish the presence of the hypothalamic hormone protirelin (thyrotropin-releasing hormone, TRH) in human thyroid and to investigate whether the concentration of this peptide in the thyroid gland is sensitive to thyroid status.

Methods: A procedure has been developed for the determination of TRH in the thyroid gland, distinct from TRH-like peptides which also react with TRH-antibody.

Results: Human thyroid was shown to contain both authentic TRH and TRH-like peptides, a similar pattern was seen in a range of animal thyroids. The concentrations of TRH in non-active goiter thyroids were substantial (41.6-248 pmol.g-1); in contrast the thyroids from hyperthyroid patients contained very little TRH (0.01-2.52 pmol.g-1).

Conclusion: The physiologic role of TRH in the thyroid is not known but the large difference between the concentrations of this hormone in non-active and hyperactive thyroids suggests that thyroidal TRH may be involved in the regulation of thyroid status.