Hello and welcome to the Zero to Finals podcast.

My name is Tom and in this episode I'm going to be talking to you about growth hormone.

And you can find written notes on this topic at zero to finals.com slash growth hormone or in the endocrinology section of the second

edition of the zero to finals medicine book. And you can find flashcards and questions to train your

knowledge on this content and help you remember the information for longer at members.0 to finals.com.

So let's get straight into it.

Growth hormone plays a central role in the growth of muscles, bones and tissues.

It also has metabolic effects and stimulates cell regeneration and proliferation.

Let's go through the growth hormone axis.

Growth hormone is controlled by two structures in the brain called the hypothalamus and

the pituitary gland, specifically the anterior part of the pituitary.

The hypothalamus produces growth hormone releasing hormone, or GHRH.

GHRH stimulates the anterior pituitary to release growth hormone, or GH.

Growth hormone acts directly on the growth hormone receptors in the tissues.

Growth hormone also stimulates the liver and some other tissues to release insulin-like

growth factor 1, or IGF1.

IGF1 travels to the tissues and acts on IGF1 receptors.

It also travels back to the brain and suppresses the hypothalamus and the pituitary,

suppressing the release of GHRH and growth hormone.

The suppressing effect of IGF1 is called negative feedback and this helps to

keep the growth hormone and the IGF1 levels within normal limits. Growth hormone is released in pulses,

notably at night time during deep sleep or slow wave sleep.

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