Adrenal Hormone Synthesis

00:01 So now what is the synthesis pathways of these various hormones.

00:05 Let's start with adrenal cortex hormones and then move into adrenal medulla hormones.

00:12 So in terms of the cortex, if we sliced the adrenal gland right in half, if you look through the various layers of the adrenal gland, we start with the capsule.

00:25 The capsule is a fibrous layer and it's mainly connected tissue.

00:29 Where we become most important with our hormone synthesis part is in the top most layer.

00:36 The zona glomerulosa.

00:38 Here is where aldosterone is synthesised.

00:42 Aldosterone is known as mineralcorticoid.

00:45 In this case mineralcorticoid is because it is involved with sodium retention which is one of our minerals.

00:51 Below this level, we have the zona fasciculata is involved with cortisol production.

01:02 This is known as a glucocorticoid.

01:05 You maybe wondering yourself, what is this corticoid portion.

01:09 That is to tell you that is part of a steroid hormone base.

01:13 In this case it was initially named glucocorticoid because it's involved with glucose metabolism.

01:21 Cortisol though is often known as a stress hormone.

01:24 It's released in times of stress and will go through all the different functions that it has.

01:31 We also have a zona reticularis.

01:34 This is where the androgens are produced.

01:37 Where the androgens are these will be things like DHEA and androstenedione.

01:46 These will be involved with secondary sex characteristics.

01:49 Finally if we go to our lower most level, this is now no longer in the cortex is the adrenal medulla.

01:56 And remember the adrenal medulla was where epineprhine is released.

02:03 Now we talk through the synthesis pathways for adrenal steroid hormones.

02:08 The biggest picture that you need to remember is you start off with cholesterol.

02:14 Cholesterol is the backbone of all these three hormones.

02:19 What's starts the process down the stairs, ATCH.

02:32 This factor release from the anterior pituitary engages an enzyme called a sideclevi enzyme.

02:38 That starts cholesterol down a number of steps process to eventually reach it's end hormone stage.

02:46 Now we will include these steps along the way in the download material so you can look at them.

02:56 But those are biochemistry related steps.

02:59 And they are more important in biochemistry than in physiology.

03:03 In physiology we are concerned with the functions that happen in these processes.

03:08 We will mention one other item and that is for aldosterone.

03:13 Aldosterone has a second regulatory step and that's that aldosterone synthase.

03:18 That's effected by angiostensin II and potassium.

03:25 The adrenal medulla also has a number of steps in the synthesis.

03:29 But pathology purposes we need to go through all of these steps because they occur in different locales within adrenal medulla.

03:38 You start off with amino acids such as tyrosine.

03:42 Tyrosine then gets converted into aldopa.

03:46 Aldopa gets converted into dopamine.

03:49 Then dopamine is transported into a chromaffin granule.

03:56 Once inside chromaffin granule it is converted to norepinephrine.

04:01 And then interestingly it's moved back out into the cytosol again.

04:06 You may ask yourself well that's odd process but it is where the enzyme is located to convert dopamine into norepinephrine.

04:16 Once you have norepinephrine out in the cytosol you use an enzyme to convert it into epinephrine.

04:23 Now it is in -- epinephrine is the form in which we're going to release it into highest quantity that's moved back into chromaffin granule.

04:34 Then it is bound in a storage complex that has primarily epinephrine about 80%.

04:44 But a little bit of norepinephrine 20%.

04:48 That is how this process works to be able to do this conversions in the right spot.

04:54 Make sure they get into a storage granule.

04:56 So that it can eventually dock and release and spill it's contents out to be picked up by the blood and deliver to peripheral tissues.

05:06 There are some transporters that are involved in this process.

05:10 These are known as VMAT transporters.

05:13 Oddly, the VMAT tranporters are fairly similar between the different types of moving either dopamine in or epinephrine out and epinephrine back in.

05:24 That is because these three modelcules, dopamine, norepinephrine and epinephrine are very, very similar in structure.