Endocrine System - Lecture Twenty Seven : Thyroid, Parathyroid and Adrenal Glands
9 important questions on Endocrine System - Lecture Twenty Seven : Thyroid, Parathyroid and Adrenal Glands
What are thyroid hormones ?
- They are different to other lipid-soluble hormones (steroid hormones) in the fact that they are made in advance and stored until required
- The hormone-receptor complex binds to DNA and acts as a transcription factor – leading to a specific protein being synthesised.
- The effects are slow to develop (hours-days)
- There are two thyroid hormones:
- T4 is the inactive form, but is produced in higher quantities
- T4 is converted to T3 when required
Explain How target cells are activated by thyroid hormones ?
- Thyroid follicles contain a protein called thyroglobulin (TGB). Iodine (from our diet) reacts with TGB molecules in the follicles.
- Iodised TGB moves to the follicular cells where thyroid hormones (T3 and T4) detach from TGB.
- Thyroid hormones are stored* in follicular cells until required
- When stimulated by thyroid stimulating hormone (TSH), T3 and T4 are secreted into the blood to target cells
- Iodine deficiency: as iodine is necessary for thyroid hormone production, a deficiency of iodine in our diet results in low levels of thyroid hormone in the body
What are the main effects of thyroid hormones?
- Growth
- Alertness
- Metabolism
- Increases body heat production (increases oxygen consumption and ATP hydrolysis)
- Stimulates fatty acid oxidation (usage of stored fat) in many tissues.
- Increases proteolysis, predominantly from muscle.
- Stimulates carbohydrate metabolism (usage of stored glucose), enhances insulin-dependent entry of glucose into cells, increases gluconeogenesis and glycogenolysis
- Higher grades + faster learning
- Never study anything twice
- 100% sure, 100% understanding
For my 1st exam I got a C. Then, I started looking for ways to learn better and I came across Study Smart. Since then I have scored a A+, A, A- and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!
I was struggling to finish all my first-year subjects for 3 years. Then I discovered Study Smart, which helped me to finish all of them within 3 months.
Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, now I usually score an A or A+.
Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!
Since using Study Smart, my average has increased significantly. I even completed a statistics course with a A+ while I'm bad at statistics. I took on extra courses this year, because of Study Smart. Thanks so much!
Ever since I started studying with StudySmart I passed all my exams !!! No more re-sits!! At first, I was happy with a pass and now I only get good grades. Many thanks!
I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.
I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on my grades, my speed and the pleasure I have in learning.
For the first time, I finally feel totally confident about the way I learn. I have the perfect overview and make great progress in terms of speed and the grades I get. Thanks, Chris!
I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..
Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a huge amount of my time on creating my summaries.
At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.
Students that study with Study Smart get better grades. The system applies all the learning methods in such a way that both well-performing students and students who struggle perform much better.
Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!
The largest effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school, Study Smart made it happen.
In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any D's. My average score is now an A and those are results I would have never had in the past
With my old method, I passed only 3 out of 8 courses. Since I started taking my notes digitally in Study Smart, I have passed all my courses on the first try. For me, StudySmart takes away the stress of wondering if I will pass or not.
Thanks to StudySmart, I passed all my exams, and with better grades than before! On top of that, I have mastered a very good study method now, which I am confident will help me earn my degree.
What are examples of thyroid hormone disorders ?
- Caused by hyposecretion of thyroid hormone
- Symptoms include low metabolic rate, weight gain, cold intolerance, lethargy, slow heart rate, growth retardation (cretinism only), hindered brain development (cretinism only)
- Caused by hypersecretion of thyroid hormone
- Symptoms include high metabolic rate, weight loss, heat intolerance, nervousness, increased heart rate, tissue swelling
Thyroid hormone negative feedback loop
- Stimulus: CNS input
- Hypothalamus: secrets thyroid releasing hormone (TRH)
- Anterior pituitary: secretes thyroid stimulating hormone (TSH)
- Thyroid gland: secrets thyroid hormones (T3 and T4)
- Effects:
- Increases body heat production (increased oxygen consumption and ATP hydrolysis)
- Adipose: increases fatty acid mobilisation
- Muscle: increases glycogenolysis and proteolysis
- Liver: increases glycogenolysis and gluconeogenesis
- Other effects: stimulates growth (foetus and early childhood), maintains normal alertness and reflexes in the nervous system
- Negative feedback : T3 and T4 negatively feedback on the anterior pituitary (decrease TSH), and the hypothalamus (decrease TRH)
What is the function and location of the parathyroid glands?
- Location : Posterior aspect of the thyroid gland
- Function: Secretes parathyroid hormone which is essential for life. It acts to increase blood calcium
Parathyroid hormone negative feedback loop
- Stimulus : low blood calcium concentration
- Parathyroid gland : secrets PTH
- Effects:
- Activate vitamin D --> increased calcium absorption from food
- Bone: increase bone breakdown (OC > OB) which increase the release of calcium into blood
- Overall response : increases blood calcium back towards the set point
- Negative feedback : normal blood calcium negatively feeds back to the parathyroid gland to reduce secretion of PTH
What is the structure, function and location of adrenal glands?
- Location : superior to each kidney
- Structure : Made up of two separate glands. Has an adrenal cortex (outer region has 3 layers) which secretes steroid hormones
- Functions :
- Middle layer : secretes cortisol
- Inner layer : secretes androgens
What is the structure and location of a thyroid gland? What hormones are made and released?
- Location : Below the larynx, on the anterior and lateral surfaces of the trachea
- Structure :
- Hormones made and released : Thyroid hormones which is essential for metabolic activity. Calcitonin hormone which is involved in calcium homeostasis
The question on the page originate from the summary of the following study material:
- A unique study and practice tool
- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
