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Steroid Hormone Receptors

by Carlo Raj, MD
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    00:02 Let’s talk about steroid hormones please.

    00:05 Now, steroid hormones, you want think of this as being a separate topic only because its mechanism is a little bit different.

    00:10 It's quite interesting here.

    00:11 You're going to like this.

    00:12 Watch.

    00:14 Let’s talk about steroid hormones, specifically adrenal cortex.

    00:16 Are we there now? Before we get to the adrenal cortex, couple of things that you want to keep in mind is when would you release or how would you release some of these hormones from the adrenal cortex.

    00:29 ACTH.

    00:30 Coming from where? Anterior pituitary.

    00:33 What’s the name of the releasing hormone? Corticotropin releasing hormone.

    00:36 Good.

    00:37 Now, ACTH is going to kick start the synthesis of your adrenocortical hormones.

    00:44 The next thing which you want to do is give yourself an acronym, right? Give yourself an acronym for the adrenal cortex.

    00:50 GFR.

    00:53 Remember, now with the adrenals, you want to divide it into two separate structures.

    00:58 What is that? The cortex and the medulla.

    01:00 The cortex and the medulla.

    01:02 The medulla is always in the inner aspect; the cortex, obviously, outer.

    01:05 The outer aspect of the adrenal is known as adrenal cortex.

    01:09 You will divide that into GF and R if you haven't done so already.

    01:13 The G stands for zona glomerulosa.

    01:16 F stands for zona fasciculata.

    01:18 R stands for zona reticularis. F stands for zona fasciculata.

    01:18 R stands for zona reticularis.

    01:20 You might've heard of the phrase, the deeper I go, the sweeter it gets.

    01:25 What am I referring to? The deeper you go, adrenal cortex, the zona reticularis, I am going to release sex hormones.

    01:36 The glomerulosa, you’re releasing what? Aldosterone.

    01:40 Mineralocorticoid.

    01:44 From your fasciculata, what are you releasing? Glucocorticoid.

    01:51 Deeper I go, sweeter it gets.

    01:53 Reticularis, I am releasing androgens.

    01:58 Where are the receptors? In general, whenever you deal with steroid hormones, these are true or false? Always, lipid soluble? True. Always lipid soluble.

    02:14 So, no matter what, your steroid hormones will always pass through the membrane.

    02:18 The next question is, where are my receptors located? Is it the cytoplasm or is it the nucleus? Here it’s the cytoplasm.

    02:27 Welcome to adrenocortical hormones.

    02:32 Mineralocorticoid, cortisol, androgen from adrenal cortex.

    02:38 Receptor located where? In the cytoplasm.

    02:42 Let’s take a look at the other column.

    02:44 Before we move on, it’s still steroid hormones.

    02:48 We just said, steroid hormones will always pass through the membrane.

    02:52 Now, where are these receptors located? Look please.

    02:56 Nucleus, nucleus, nucleus.

    02:58 These include estrogen – oh, my goodness, estrogen.

    03:02 We’ll talk about what estrogen quite a bit.

    03:04 How important is that hormone? Quite.

    03:08 Not just in a female, but then in a male too and especially as we get into our gonadal pathology. but then in a male too and especially as we get into our gonadal pathology.

    03:14 Thyroid hormone receptor.

    03:16 Thyroid hormone.

    03:17 Would you tell me what is the predominant thyroid hormone that is released? By predominant, I mean greater concentration of your thyroid hormone being released in the anterior pituitary, by far, it's T4.

    03:30 They’re not going to ask you how much.

    03:32 It could be maybe 20 to 1 ratio, 15 to 1 ratio, whatever.

    03:36 The point is you’re releasing excessive T4.

    03:41 The active type of thyroid hormone, of course, is T3.

    03:45 We’ll talk about that in greater detail.

    03:48 Vitamin D.

    03:49 From henceforth, you want to think of vitamin D as being a hormone.

    03:54 Vitamin D, what does it do? Active type.

    03:58 Where is active type of vitamin D being synthesized? Go back to nephrology.

    04:03 In your proximal convoluted tubule, what was the name of the enzyme in the PCT in the – to activate your vitamin D? Good.

    04:11 1α-hydroxylase.

    04:13 What's that active form of vitamin D called? Do not ever forget that.

    04:16 It's also called calcitriol.

    04:19 Keep going.

    04:20 What is the name of the hormone that's responsible for stimulating that enzyme in the PCT? It’s PTH.

    04:26 All of that, as you know, is incredibly important.

    04:29 Do not forget that.

    04:30 Because if you’re going to renal failure, that enzyme known as 1α-hydroxylase can never be stimulated by PTH.

    04:36 Hence your patient with renal failure will always be hypocalcemic.

    04:40 And always have what kind of hyperparathyroidism? Secondary, secondary, secondary, secondary, secondary.

    04:47 Then we have retinoic acid receptor.

    04:51 Put these two together.

    04:53 Vitamin D, vitamin A.

    04:55 Vitamin D, vitamin A.

    04:56 That’s retinoic acid, isn’t it? A type of vitamin A.

    05:01 So, both of these vitamins, you want to think of as being a lipid soluble, passes through the membrane.

    05:08 It works in the nucleus, so that it can bring about particular effects.

    05:13 With vitamin D, let’s say that you go into the GI and intestine.

    05:17 It's going to work upon – work in the nucleus, so that you up-regulate what’s known as calcium-binding protein (CBP).

    05:24 That calcium-binding protein obviously responsible for reabsorption of calcium.

    05:30 And in pathology, when you don't have vitamin D for whatever reason, you are rendered as an adult osteomalacia.

    05:38 And if it's a child, welcome to rickets, right? And then what about retinoic acid? Remember WBC pathology.

    05:45 What was the translocation that we saw, with acute myelogenous leukemia type 3, M3, that up-regulates retinoic acid receptor? Good. 15, 17.

    06:00 Well, how do you use this to your advantage? Use the ATRA (all-trans retinoic acid).

    06:05 Remember? If you don't, go back and take a look.

    06:08 All of this is crucial.

    06:09 Put things together.

    06:11 It works upon retinoic acid receptor, so that it can do what? It works upon retinoic acid receptor, so that it can do what? So that you can properly mature yourselves.

    06:17 So, therefore, if a patient doesn't have vitamin A, that patient is rendered blind.

    06:25 What kind? Colorblindness.

    06:27 And if vitamin A isn't present, tell me about the conjunctiva.

    06:32 It doesn't properly mature.

    06:33 Welcome to keratoconjunctivitis.

    06:36 Clear? Important.


    About the Lecture

    The lecture Steroid Hormone Receptors by Carlo Raj, MD is from the course Introduction to the Endocrine System.


    Included Quiz Questions

    1. Zona fasciculata - glucocorticoid receptor
    2. Zona glomerulosa - glucocorticoid receptor
    3. Zona fasciculata - mineralocorticoid receptor
    4. Zona reticularis - mineralocorticoid receptor
    5. Zona glomerulosa - androgen receptor
    1. Androgen receptor
    2. Estrogen receptor
    3. Vitamin D receptor
    4. Thyroid hormone receptor
    5. Retinoic acid receptor
    1. Vitamin D - calcitriol
    2. Thyroid hormone - T4
    3. Vitamin D - PDH
    4. Estrogen - prolactin
    5. Thyroid hormone - retinoic acid
    1. Retinoic acid receptor
    2. Vitamin D receptor
    3. Androgen receptor
    4. Mineralocorticoid receptor
    5. Glucocorticoid receptor

    Author of lecture Steroid Hormone Receptors

     Carlo Raj, MD

    Carlo Raj, MD


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