Thyrotropin releasing factor

Thyrotropin-releasing factor (TRF) = thyrotropin-releasing hormone (TRH) = thyroliberin. 

Many small peptides exert their effects at very low concentrations. For example, a number of vertebrate hormones (Chapter 23) are small peptides. These include oxytocin (nine amino acid residues), which is secreted by the posterior pituitary and stimulates uterine contractions bradykinin (nine residues), which inhibits inflammation of tissues and thyrotropin-releasing factor (three residues), which is formed in the hypothalamus and stimulates the release of another hormone, thyrotropin, from the anterior pituitary gland. Some extremely toxic mushroom poisons, such as amanitin, are also small peptides, as are many antibiotics. 

Schally AV, Redding TW (1967) In vitro studies with thyrotropin releasing factor. Proc Soc Exp Biol Med 126 320-325 Vale W, Grant G, Amoss M, Blackwell R, Guillemin R (1972) Culture of enzymatically dispersed anterior pituitary cells Functional validation of a method. Endocrinology 91 562-572... 

In amino acids 3/(C0-Cv) varies between 1-5 and 3-5 Hz. (57, 58) For the proline residue in the tripeptide hormone thyrotropin-releasing factor (TRF, LGlu-His-Pro-NH2) Haar et al. (60) report that 3/(C0-Cy) <0-5 and 37(Ca-Cg) = 3-9 Hz. Using the angular dependence of 3/(C-C) predicted by Barfield et al., (66, 52) Haar and co-workers (60) conclude that the proline residue in TRF is preferentially in the endo conformation in contrast to proline itself. 

Thyrotropin-releasing factor (TRF) is produced in the hypothalamus and arrives at the pituitary via the hypophyseal portal blood system. TRF mediates the release of thyrotropin from the anterior hypophysis. The thyrotropin release is inhibited by thyroxine, presumably free thyroxine, and the inhibition is dose dependent. Thus excessive levels of thyroxine depress thyrotropin release, and lower thyroxine levels result in increased thyrotropin release from the anterior pituitary. TSH, in turn, stimulates thyroid hormone synthesis and secretion by the thyroid gland. Thyroxine and triiodothyronine are bound to specific binding proteins in the blood. The amounts and binding constants of the specific thyroid-binding proteins, together with the rate of thyroid hormone release from the thyroid, determine the amount of free thyroxine in the blood. Free thyroxine levels are determined not only by the rate of... 

B14. Bowers, C. Y., Redding, T. W., and Schally, A. V., Effect of thyrotropin-releasing factor (TRF) of ovine, bovine, porcine and human origin on thyrotropin release in vitro and in vivo. Endocrinology 77, 609-616 (1965). 

B15. Bowers, C. Y., Schally, A. V., Reynolds, G. A., and Hawley, W. D., Interactions of 1,-thyroxine or L-triiodothyronine and thyrotropin-releasing factor on the release and synthesis of thyrotropin from anterior pituitary gland of mice. Endocrinology 81, 741-747 (1967). 

E7. Etkin, W., and Gona, A. G., Failure of mammalian thyrotropin-releasing factor preparation to elicit metamorphic responses in tadpoles. Endocrinology 82, 1067-1068 (1968). 

Sinha, D., and Meites, J., Effects of thyroidectomy and thyroxine on hypothalamic concentration of thyrotropin releasing factor and pituitary content of thyrotropin in rats. Neuroendocrinology N. Y.) 1, 4-14 (1965). 

W2. Wilber, J. F., and Utiger, R. D., In vitro studies on mechanism of action of thyrotropin-releasing factor. Proc. Soc. Exptl. Biol. Med. 127, 488-490 (1968). 

The conformational analysis of several linear proline-containing hormones has been considerably aided by 1 3C nmr studies. The ratio of cis- and trans-isomers and the spin lattice relaxation times of thyrotropin-releasing factor or hormone (TRF or TRH), L-pyro-glutamyl-L-histidyl-L-prolinamidc, in deuterium oxide, deuterated dimethyl sulfoxide and deuterated pyridine have been determined... 

Deslauriers, R., McGregor, W. II., Sarantakis, D., and Smith, I. . P. (1974). Biochemistry 13, 3443. Carbon-13 Nuclear Magnetic Resonance Studies of Structure and Function in Thyrotropin-Releasing Factor. Determination of the Tautomeric Form of Histidine and Relationship to Biology Activity. Deslauriers, R., Paiva, A. . M., Schaumburg, K., and Smith, I. . P. (1975). Biochemistry 14, 878. Conformational Flexibility of Angiotensin II. A Carbon-13 Spin-Lattice Relaxation Study. 

Fig. 8. Relationship between 20-minute level of serum thyroid-stimulating hormone (TSH) after 200 ng of thyrotropin-releasing factor (TRH) i.v. and the 6-hour thyroidal uptake after one week on triiodothyronine (Ts). 100 /ig daily.

J. Rivier, Total synthesis of the hypothalamic thyrotropin releasing factor. Methods Enzymol. 37 (Pt.B) 408-415 (1975)... 

Prolactin releasing factor (PRF), prolactin releasing hormone, prolactoliberin a hormone thought to be identical with thyrotropin releasing factor, llie structure of Prolactin release inhibiting hormone (PIH) (prolactostatin) is unknown. PRF promotes, whereas PIH inhibits the synthesis and secretion of prolaction by the anterior pituitary. 

Lechan, R. M., Alpert, L. C., and Jackson, I. M. D., 1976, Synthesis of lutenizing hormone releasing factor and thyrotropin releasing factor in glutamate-lesioned mice. Nature 264 463-465. 

Blagdon, D.E., Rivier, J., Goodman, M. Proposed tertiary structure for the hypothalamic thyrotropin-releasing factor. Proc. nat. Acad. Sci. (Wash.) 70, 1166(1973)... 

Fleischer, N., Lorente, M., Kirkland, J., Kirkland, R. Synthetic thyrotropin releasing factor as a test of pituitary thyrotropin reserve. J. din. 208. Endocr. 34, 617-624 (1972)... 

---