Thyroid and Parathyroid Glands

by Jason Amores Sumpter
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The thyroid gland is an endocrine gland that's involved in the regulation of metabolic rate and calcium homeostasis. Now thyroid hormones, of which there are two commonly referred to as T three and T four are synthesized from tyrosine, making them mean hormones. However, they act like steroid hormones because of the iodine attached to their structures, which essentially shield the molecule. And these two different thyroid hormones are. Our purpose is going to be treated the same. I mean, they largely have the same effects. However, there are two different types, and you should be aware there are two different structures, and their structures differ in that. T three has three iodine atoms and t four has four. I Dine Adams so pretty easy to remember there now, the thyroid hormones T three and T four have a wide range of effects, but generally they're going to affect metabolic rates, heart rate and heat production in the body, which is actually pretty pretty intricately linked to these other rates. Now thyroid hormones are going thio act in a negative feedback loop, and they're going to block the release of thyroid trope in releasing hormone from the hypothalamus and thyroid stimulating hormone from the anterior pituitary. So really nice negative feedback loop here, where the downstream product, so to speak of this chain of events will feedback and shut off the release of the hormones that stimulate its release. Very clean negative feedback loop there. Now the parathyroid gland is going to be involved in calcium homeostasis along with the thyroid. They each kind of secrete a hormone that eyes counterbalance to the other. So the parathyroid glands actually kind of sit on the thyroid more or less. They're not as distinct as the thyroid, so they're kind of hard to picture. But they're going to release parathyroid hormone, which is gonna act in opposition Thio calcitonin. So first, let me talk about parathyroid hormone, and then I'll get back to calcitonin. So parathyroid hormone is going to essentially try to increase calcium levels in the blood when it did, when it detects low, or when the body detects low calcium levels, it's going to secrete this hormone, and that's going to cause the bones to get re absorbed, which is going thio, extract calcium from the bone and put it in the bloodstream. It's also going to decrease calcium excretion in the kidneys, meaning that the body is going to retain mawr calcium. Additionally, it increases calcium absorption in the gut, so your body is going to get more efficient at, uh, taking in the calcium from the food you eat. So this all serves to raise blood calcium levels. However, Calcitonin works in opposition to that. This is, ah, peptide hormone that's secreted by the thyroid, and it's going to be secreted in response to high levels of calcium in the blood. And what it's gonna do is essentially increased calcium storage in the bone. So opposite effect. From that right, it's. Instead of pulling calcium out of the bone, it's gonna start depositing calcium into the bone. And it's also going to increase, uh, calcium excretion in the kidneys. So again, opposite of that, it's going to make sure that the body gets rid of more calcium because it has too much. Lastly, it's going to decrease calcium absorption in the gut, so opposite effect of that these two hormones work to balance each other out Calcitonin. The way to remember what it does is it tones down calcium, so tones down calcium and remember that calcitonin is secreted by the thyroid on parathyroid hormone is secreted by the parathyroid. With that, let's flip the page