T3's effcet on GH

Here's some info I pulled from my notes on t3's effects on Growth Hormone.

The regulation of growth hormone (GH) by thyroid hormones (TH) has been shown to present species variation. We investigated the regulation of GH in the eel, representative of an ancient group of teleosts. In vivo administration of triiodothyronine (T3) or thyroxine (T4) significantly reduced pituitary and serum GH levels, as measured by homologous RIA. In order to investigate the ability of TH to regulate GH production directly at the pituitary level, we used a long term, serum-free primary culture of eel pituitary cells. Both T3 and T4 inhibited GH release in a concentration-dependent manner, producing up to 50% of inhibition at 10 nM, with an ED50 of<0.2 nM, within the range of their physiological circulating levels. Other hormones also acting via the nuclear receptor superfamily, such as sex steroids (testosterone, estradiol and progesterone) and corticosteroid (cortisol), had no effect on GH release in vitro, underlining the specificity of TH regulatory effect on GH. Measurement of both GH release and cellular content for calculation of GH production in vitro indicated that TH not only inhibited GH release but also GH synthesis. Dot blot assay of GH messenger RNA (mRNA) using a homologous eel cDNA probe showed a decrease in GH mRNA levels in cells cultured in presence of T3, as compared with control cells. This demonstrated that the inhibition of T3 on GH synthesis was mediated by a decrease in GH mRNA steady levels. In conclusion, we demonstrate inhibitory regulation of eel GH synthesis and release by TH, exerted directly at the pituitary level. These data contrast with the rat, where TH are known to have a stimulatory effect and suggest that the pattern observed here in an early vertebrate and also found in birds, reptiles and some mammals including humans, may represent an ancestral and more generalized vertebrate pattern of TH regulation of pituitary GH.

Good stuff. Conversely, GH also suppresses TH, due to both being negatively regulated by somatostatin (TH to a lesser degree than GH).

Also, this study is interesting in that it refutes the argument for nolva to suppress IGF-1 levels.....because, it says that estradiol in pituitary cells does NOT affect GH production, which contradicts the very mechanism of action that was hypothesized to explain nolva's ability to reduce IGF-1 levels.

In contrast to most vertebrates, GH reportedly has no effect upon somatic growth of the chicken (c). However, previous studies employed only 1-2 dosages of the hormone, and limited evidence exists of a hyperthyroid response that may confound its anabolic potential. This study evaluated effects of 0, 10, 50, 100 and 200 mg/kg BW/d cGH (0-200GH) infused i.v. for 7 days in a pulsatile pattern to immature, growing broiler chickens (9-10 birds/dosage). Comprehensive profiles of thyroid hormone metabolism and measures of somatic growth were obtained.

Overall (average) body weight gain was reduced 25% by GH, with a curvilinear, dose-dependent decrease in skeletal (breast) muscle mass that was maximal (12%) at 100GH. This profile mirrored GH dose-dependent decreases in hepatic type III deiodinase (DIII) activity and increases in plasma T3, with both also maximal (74 and 108%, respectively) at 100GH. No effect on type I deiodinase was observed. At the maximally effective dosage, hepatic DIII gene expression was reduced 44% versus controls. Despite dose-dependent, fold- increases in hepatic IGF-1 protein content, circulating IGF-1 was not altered with GH infusion, suggesting impairment of hepatic IGF-1 release. Significant, GH dose-dependent increases in plasma NEFA and glucose, and overall decreases in triacylglycerides were also observed. At 200GH, feed intake (FI) was significantly reduced (19%; P<0.05) versus controls, however, additional control birds pair-fed to this level did not exhibit any responses observed for GH birds.

The results of this study support a pathway by which GH impacts on thyroid hormone metabolism beginning at a pretranslational level, with reduced hepatic 5DIII gene expression, translating to reduced protein (enzyme) expression, and reflected in a reduced level of peripheral T3-degrading activity. This contributes to decreased conversion of T3 to its inactive form, thereby elevating circulating T3 levels. The hyper-T3 state leads to reduced net skeletal muscle deposition, and may impair release of GH-enhanced, hepatic IGF-1.

In conclusion, GH has significant biological effects in the chicken, but profound metabolic actions predominate that may confound positive, IGF-1-mediated skeletal muscle growth.

**** you guys are making my feel bad, haven't had time to do research so I can't contribute, so thanks for the info.

JohnnyB

layman terms anyone?

Might be advisible to supplement some thyroid when taking gh to prevent suppression. Learn from my mistakes suppression from gh and low caloires does and will happen. My thyroid levels are all fine in upper 2/3 levels but t-3 is at bottom end and **** drs will not do anything to help me becuase I am in the range. I have tried every thing from tyrosine, gugguls, kelp, coelskins, thyrotropin, 4 TBSP cocconut oil (standard processes) and nothing is working. Temperatures are around 97 degrees in the morning waking up and I freeze all day long, lost 20 lbs of muscle, gained alot of abdominal fat. Metabolsim is about 40% then normal but drs say I am fine. Least resort is either trying armour thyroid or some t-3 and monitoring my temperature to try to see if I can reset it some how. I have been to 5 different drs and they won;t do anything. t-3 80 (60-220). Any help be much appreciated

Have you tried Coleus forskolii and t-100X is the strongest supplement going IMO for regulating thyroid fucntion, if your BBT still doesn't get to atleast the mid 97,s then you need to consider your adrenal function, this is the second key at optimizing metabolic function.

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Originally Posted by hardasnails1973

Might be advisible to supplement some thyroid when taking gh to prevent suppression. Learn from my mistakes suppression from gh and low caloires does and will happen. My thyroid levels are all fine in upper 2/3 levels but t-3 is at bottom end and **** drs will not do anything to help me becuase I am in the range. I have tried every thing from tyrosine, gugguls, kelp, coelskins, thyrotropin, 4 TBSP cocconut oil (standard processes) and nothing is working. Temperatures are around 97 degrees in the morning waking up and I freeze all day long, lost 20 lbs of muscle, gained alot of abdominal fat. Metabolsim is about 40% then normal but drs say I am fine. Least resort is either trying armour thyroid or some t-3 and monitoring my temperature to try to see if I can reset it some how. I have been to 5 different drs and they won;t do anything. t-3 80 (60-220). Any help be much appreciated

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Originally Posted by BIGCHEST1225

layman terms anyone?

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Get a medical dictionary:lol:

JohnnyB

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Originally Posted by einstein1905

Good stuff. Conversely, GH also suppresses TH, due to both being negatively regulated by somatostatin (TH to a lesser degree than GH).

Also, this study is interesting in that it refutes the argument for nolva to suppress IGF-1 levels.....because, it says that estradiol in pituitary cells does NOT affect GH production, which contradicts the very mechanism of action that was hypothesized to explain nolva's ability to reduce IGF-1 levels.

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Very true, BUT although maybe not through the mechanism they concluded Nolva DOES suppress IGF-levels both in rats and tested adult Men.
(They measured nmol/kg of bodyweight)

You of all people should know that the body has countless feedbackstreams most are even unknown YET (though many people believe medics have all the questions but are unwilling to share --> if they knew how little we know they probably wouldn't even come to us any more) so IGF production must be suppressed in some other manner.

Greets
Kingofmasters