Thyrotropin-Releasing Hormone Stimulates Body Weight Gain and Increases Thyroid Hormones and Growth Hormone in Plasma of Cockerels

Abstract

The effect of TRH on growth in 4-week-old cockerels was examined in two separate experiments. Daily injection of TRH via the brachial vein stimulated growth in 4-week-old cockerels over 17 days of treatment in the first experiment and over 25 days in the second. In the first experiment, TRH at 1.0 micrograms and 10.0 micrograms/bird caused significant (P less than 0.05) increases of 12.0% and 12.4%, respectively, in growth rate, whereas in the second experiment, only the 1.0 micrograms/bird level of TRH caused an increase (P less than 0.05). In each experiment, the increase in body weight gain was not TRH dose dependent, and neither feed consumption nor feed efficiency was affected. Possible involvement of pituitary hormones in TRH-stimulated growth in cockerels was studied in a separate experiment, and the effects of TRH on plasma T3, T4, and GH were examined. TRH was given iv at 0.1, 1.0, and 10.0 micrograms/bird daily for 5 days, and plasma T3, T4, and GH concentrations were measured 15, 60, and 180 min postinjection by RIA on days 1, 3, and 5. The responses of T3 and T4 to TRH were greatest on day 1, were diminished by days 3 and 5, and were not dose-related. Significant, not dose-related, elevations of plasma GH concentrations were obtained at all doses of TRH. Based on these results, we suggest that TRH has the ability to promote a significant increase in body weight gain in 4-week-old cockerels, and the stimulatory effects may be mediated through GH and/or thyroid hormones.

Localization of mRNA Encoding Thyrotropin-Releasing Hormone Precursor in the Brain of Sockeye Salmon

“…TRH also stimulated release of prolactin (PRL) and α-melanocyte-stimulating hormone (α-MSH) in amphibians (Toron et al, 1983;Seki and Kikuyama, 1986). In birds, TRH elevated plasma levels of thyroid hormones and growth hormone (GH) (Leung et al, 1984). Actions of TRH in fishes are more confusing (see Crim et al, 1978).…”

The influence of thyrotropin-releasing hormone (TRH) on growth rate and thyroid activity in broiler chicks

“…injections of TRH for 17 days promoted weight gain of 28-day old cockerels by about 12% (Leung et al, 1984). In experiment 1 relative body weight gain of TRH-treated 28-day old małe chickens increased by 5.7% after the 10-days and by 10% after the 20-days treatment.…”

“…In females, TRH had no effect on growth parameters. Previous observations on chickens (Harvey et al, 1978;Burkę, 1983;Leung et al, 1984;Lauterio and Scanes, 1987) and ducks (Folzer-Joudaione et al, 1988) established that TRH not only stimulates the release of thyroid hormones but also is a potent stimulant of GH secretion. Remarkable differences in GH response between małe and female broilers were seen in the form of higher plasma GH concentrations in males (Harvey et al, 1977;Johnson et al, 1990).…”

“…The results of studies by Leung et al (1984) indicated that daily iv. injection of 1 or 10 fig TRH/chick for 17 days increased the growth rate of 28-day old male chickens by about 12% compared with saline injected controls.…”

“…Significant non-dose-related increase of plasma T 3 and T 4 concentrations were observed. Peak circulating hormone levels appeared 1 h after TRH injection (Leung et al, 1984;Kahl and Rz^sa, 1980;Kiihn et al, 1991). On the other hand in the experiment of Buonomo and Baile (1986) daily iv.…”