USMLE Why on earth does GH (growth hormone) ↑ insulin resistance? Is it contradictory?

[LichenPlanus]

If GH ↑ insulin resistance -> ↓ TK -> ↓ RAS/MAP -> ↓ cell growth (FA pg 314 & 317)- HOW do you get increased linear growth and muscle production, if the insulin dependent tissues using GLUT 4 such as skeletal muscle (FA pg 314), are not responding enough to insulin because of ↑ resistance?

Additionally, if GH release is ↑ during sleep, but Ghrelin also ↑ GH (and Ghrelin is increased when you are sleep deprived -pg 317-), does that mean GH ↑ if you sleep or not sleep?

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[mastermind8490]

As far as I know, GH induces skeletal growth and muscle hypertrophy via IGF-1, independent of it's effect on insulin resistance.

From Wiki: "IGF-1 is a primary mediator of the effects of growth hormone (GH). Growth hormone is made in the anterior pituitary gland, is released into the blood stream, and then stimulates the liver to produce IGF-1. IGF-1 then stimulates systemic body growth, and has growth-promoting effects on almost every cell in the body, especially skeletal muscle, cartilage, bone, liver, kidney, nerves, skin, hematopoietic cell, and lungs. In addition to the insulin-like effects, IGF-1 can also regulate cell growth and development, especially in nerve cells, as well as cellular DNA synthesis"

As for GH and Ghrelin ... ¯\_(ツ)_/¯ ... but general consensus is that GH increases w/ sleep.

 

[LichenPlanus]

As far as I know, GH induces skeletal growth and muscle hypertrophy via IGF-1, independent of it's effect on insulin resistance.

I really appreciate the reply, it seems that would be the only logical thing. Although FA 321 says IGF-1 and Insulin are both Intrinsic Tyrosine Kinases, their receptors/different affinities for insulin vs IGF-1.

As for ghrelin (increasing GH when no sleep) & sleep both ↑ GH - I will post if I find any explanation.

Thanks again.

 

[pd1112]

The effect of increased insulin resistance is something that occurs after longstanding GH excess (GH-secreting tumor, exogenous use). GH/IGF-1 increase blood glucose which stimulates insulin release to increase glucose uptake in the liver (for glycogenesis) & increase amino acid uptake in skeletal muscle and other anabolic pathways. With longstanding excess -> chronic insulin release -> insulin resistance of tissues.

Growth hormone is normally released during sleep because it's an appropriate time for anabolism when your energy demands are low. It's released "pathologically" with sleep deprivation via ghrelin because it's immediate effects are increased blood glucose & amino acids, which is beneficial during a stress condition in the same way that epi/glucagon/cortisol are beneficial.

Essentially all of the endocrine hormones work in a big feedback circle, so if you think about it too much, they're all both stimulating & inhibiting each other. Don't do it.

 

[aspiringmd1015]

gh's a stress hormone, bottomline. Functions to increase blood glucose so your brain can use it. i didnt read the baove posts, but the "insulin-like" effects of igf are only in regard to their protein effects.

 

[aspiringmd1015]

read brs, has this stuff given in an organized fashion

 

[LichenPlanus]

mastermind, PD, and aspiring MD - really appreciate you answering my question. I'm gonna go ahead and read BRS today as well - thanks for the recommendation.