Health and medicine
Hormone concentration metabolism and negative feedback
In this video we're going to learn about how the concentration of hormones in our blood is regulated. By Ryan Patton. . Created by Ryan Scott Patton.
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- Is the double negative feedback of both the pituitary and the hypothalamus a safety factor? If one of them fails then the other one still does the job?(3 votes)
- I actually have never heard of that. The Hypothalamus practically controls the anterior pituitary gland. For example, if the hypothalamus makes CRH (Corticotropin-releasing hormone), this hormone stimulates the pituitary gland to produce ACTH (Adrenocorticotropic Hormone) which will stimulate the adrenal glands to produce all sorts of hormones such as cortisol. Hypothalamus produces "releasing hormones" that go to the pituitary gland and stimulate the production of "stimulating hormones" which are released into the body to target specific organs that produce very specific hormones, such as the adrenal gland producing cortisol. A feedback system usually involves 1) hypothalamus, 2) pituitary gland, and 3) Organ. If there is too much cortisol being made, this could send a negative feedback stimulus to both the pituitary gland (to stop secreting ACTH) and to the hypothalamus (to stop secreting CRH).(8 votes)
- Can you please tell me why it is called Negative? And how different is it from hormone concentration mechanism? Thanks a tonn.....(2 votes)
- If you're talking about the negative feedback loop at1:44, "negative" as opposed to "positive" feedback loops describe any process that regulates itself.
For example, think of a thermostat in your house. It has a sensor that knows the temperature. Then it heats the house. When the temperature rises, it triggers the sensor, which turns the heater off.
Blushing in embarrassment, however, is a positive feedback loop. You blush because you are embarrassed. The blushing causes you to be more embarrassed and you blush more.(5 votes)
- Could you elaborate on the negative feedback of cortisol with the adrenal cortex and how levels of ATCH and CRH are changed(2 votes)
- When cortisol is released from the adrenal cortex, this will increase the concentration of cortisol in circulation. This increase will be sensed by neurons in the hypothalamus of the brain. The cortisol will bind to receptors on a neuron in an area of the hypothalamus called the Paraventricular Nucleus. The binding of cortisol will signal these neurons to stop releasing CRH (so the levels of CRH secretion will go down), Normally, this CRH would be moving down to the anterior pituitary and signaling it to secrete ACTH. So the decrease in CRH release results in a decrease in ACTH release from the pituitary. (also, cortisol will bind to receptors in the pituitary itself and decrease ACTH release directly, doubling down on the inhibition of ACTH release).
As a result of all this, there will be less ACTH in the circulation. Because the normal role of ACTH is to stimulate the adrenal glands to produce cortisol, the decrease in ACTH will result in decreased cortisol production.
So all in all the release of cortisol will eventually (through decreases in CRH and ACTH) decrease the release of more cortisol.(3 votes)
- How does the hypothalamus and pituitary gland turn back "on" and begin to release TRH and TSH again? How does a receptor sense an absence of hormone in the blood?(1 vote)
- They don't need to. The cells just try to make their signalling hormones all the time, because they know the whole body needs the thyroid hormones to work properly. The receptors only need to put the brakes on when there's enough thyroid hormone, so the cell never needs to be able to detect that levels are low.(4 votes)
- Hi, can you please explain how an excess in prolactin can effect men's fertility. An excess in prolactin can make men hypogonadal, however I can't find information that explains why this happens. It doesn't make sense why an excess in prolactin would effect testosterones feedback loop. An explanation would be great.(1 vote)
Thanks for this interesting question. Above is an article you may enjoy. Short answer, high levels of prolactin in men are typically due to a tumor or abnormal growth of the pituitary gland (some medications may also cause this). In some men, excess prolactin decreases the amount of GnRH, gonadatropin releasing hormone made by the Hypothalamus which then decreases the amount of FSH and LH made by the anterior pituitary so the testes become smaller.
(My thoughts- 1. The area of erectile dysfunction is an area of present research and more information may become available in a journal search. 2. Hormones are more complex and interrelated then may be apparent, and the consequence of hormonal excess or deficit may be difficult to predict.)(4 votes)
- Does the hormone concentration of pregnant women affect the cell growth/metabolism and birth weight of their baby?(1 vote)
- Some of the maternal hormones affect cell growth in fetus e.g. high estrogen level during pregnancy causes maternal thyroxine to be secreted, which then cross placenta and into the fetal domain, and is essential for normal development of fetal brain . But most of the hormones e.g. insulin required by the fetus for development are secreted by the fetus itself .
High levels of glucocorticoids produced during pregnancy by the consumption of alcohol disturbs fetal development.(3 votes)
- Hi, is there any difference between the receptors on the hypothalamus and pituitary in terms of amount or affinity for T3 and thyroxine so that this whole negative feedback loop can function more precisely and accurately since the hormone concentration is so important?(2 votes)
- how many types or hormones are there(1 vote)
- 3: peptide, steroid, and amino-acid derivative(2 votes)
- Can you please explain why you need negative feedback also for the pituitary gland and not only for the hypothalamus?(1 vote)
- For negative feedback is the hormone binding to the hypothalamus and pituitary gland to stop production?(1 vote)
When we talk about the endocrine organs and the endocrine glands and we talk about hormones flying all throughout the body, it's pretty easy to develop this mental image of that process happening pretty haphazardly. And so you can imagine hormones just coursing all throughout the body, being fired at will and to everywhere. But if you think about the effects of the endocrine glands, like in the adrenal glands with the fight or flight hormones, it becomes pretty important that the effects being stimulated by these hormones be well controlled because our body is pretty sensitive to those effects. And so it turns out that the hormone concentration in our blood at any given time is pretty tightly controlled. And one of the ways that it's controlled is through this idea of metabolism and excretion. And so for every hormone that reaches its receptor, thousands more are swept up and removed by the body. And one of the ways that to remove this through the liver. And the liver will metabolize extra hormones and turn them into bile, which is ultimately excreted in the digestive system. And another organ is the kidney. And you have two of these. And they're filtering your blood all of the time. And they're removing waste products from the blood through urine. And then some hormones are actually just broken down in the blood. And then at the products of that breakdown flow into the liver or the kidneys. And then sometimes you can even sweat these hormones out. But the idea here is that all of the time for all the hormones reaching the receptors, a lot are swept up and removed from the body. And another way that concentrations of hormones in the body are controlled are through feedback loops. And the majority of feedback loops are what we consider to be negative feedback loops. And the idea behind negative feedback loops is that conditions resulting from the hormone action suppress further releases of those hormones. And that can be a pretty confusing idea. So I'm going to draw an example. So we have the hypothalamus here. I'm going to draw it in. And I'll write it down. And the hypothalamus releases a hormone, thyroid-releasing hormone-- so TRH. And it releases it. And it goes down to the pituitary gland, which I'll drawn in, in right here. And in response to TRH, the pituitary gland releases thyroid-stimulating hormone or TSH. And TSH goes down to the thyroid glands, which would be about right here. And the thyroid gland releases its hormones, T3, or triiodothyronine, and throxine. And these thyroid hormones travel all throughout the body in search of the receptors in order to, let's say, up-regulate metabolism. That's one of the major jobs of the thyroid glands. And so here's where the idea becomes pretty cool. Because some of the receptors are located on the pituitary gland and the hypothalamus. And as the thyroid hormones reach the pituitary and the hypothalamus, they signal the hypothalamus and pituitary gland to stop making their hormones. And the hypothalamus and pituitary gland see that we have enough thyroid hormones in the blood and that they don't need to make any anymore. And so this is a major way that the thyroid hormone levels in the body are controlled. And you might say, hey, that sounds a little bit redundant. I mean if the hypothalamus can be turned off by the thyroid hormones and it's upstream from the pituitary gland, then why does the pituitary gland even have to have these receptors? But the redundance is really just a reflection of how important feedback control is and how important the concentration of hormones in the body is. And so hopefully what we can see is that the hormone levels in the body aren't haphazard and aren't willy-nilly. And that concentration is important.