Clinical Significance:
Thyrotropin Releasing Hormone (TRH) is a tripeptide produced primarily by the hypothalamus. TRH is produced from a prohormone which contains multiple copies of the TRH molecule meaning that several TRH entities can be released from one precursor. It has a stimulatory effect on the pituitary releasing Thyrotropin (TSH). TRH secretion is controlled in a negative feedback system by thyroid hormones. Binding of TRH to its receptor causes a rise in calcium which initiates TSH secretion. It also stimulates adenyl cyclase in the pituitary. TRH also stimulates secretion of Prolactin, Growth Hormone in Acromegaly, and ACTH in Cushing’s and Nelson’s Syndromes. Levels of TRH are non-detectable or very low in patients with Hyperthyroidism and Hypothalamic Hypothyroidism. Levels are elevated in patients with Primary and Pituitary Hypothyroidism
Reference Range:
Up to 40 pg/ml
Procedure:
Thyrotropin Releasing Hormone is measured by direct radioimmunoassay.
Patient Preparation:
Patient should not be on any thyroid medication, if possible, for at least 48 hours prior to collection of specimen.
Specimen Collection:
Collect 10mL blood in the special TRH preservative tube filling tube completely and separate as soon as possible. Freeze specimen immediately after separation. Minimum specimen size is 1 ml. Special TRH preservative tubes are available from Inter Science.
Important Precaution:
Thyrotropin Releasing Hormone must be collected with the TRH Preservative. No other specimen is acceptable.
Special Specimens:
For tumor/tissue and various fluids (i.e. CSF, peritoneal, synovial, etc.) contact the Institute for requirements and special handling.
Shipping Instructions:
Ship specimens frozen in dry ice.
References:
1. MM Kaplan, JA Taft, S Reichlin, and TL Munsat. Sustained Rises in Serum Thyrotropin, Thyroxine, and Triiodothyronine during Long Term, Continuous Thyroid Releasing Hormone Treatment in Patients with Amylotrophic Lateral Sclerosis. Journal of Clinical Endocrinology and Metabolsim 63: 808, 1986.
2. GE Shambaugh III, JF Wilber, E Montoya, H Ruder, and ER Blonsky. Thyrotropin-Releasing Hormone (TRH): Measurement in Human Spinal Fluid. Journal of Clinical Endocrinology and Metabolism 41: 131, 1975.