Lecture 29: Glucose metabolism, energy balance and obesity Flashcards
Describe the brain pituitary thyroid axis
In the hypothalamus, there is the paraventricular nucleus with neurosecretory cells that project to the median eminence and these cells produce thyroid releasing hormone. This is released into the portal capillary vasculature in the anterior pituitary gland. Here, we find thyrotropes that release thyroid stimulating hormone. TSH stimulates the release of thyroid hormone from the thyroid
What are the two types of thyroid hormone?
T3 (triiodothyronine)
T4 (thyroxin)
Of the two thyroid hormones, which is the metabolically active one?
T3
How does thyroid hormone regulate its secretion?
T3 negatively feedsback onto the anterior pituitary gland to stop the release of thyroid stimulating hormone and to the hypothalamus to stop the release of thyroid release hormone
How is T4 converted to T3?
one of the iodines is cut off and now it is metabolically active
How does thyroid hormone affect the cell?
T3 binds to an intracellular nuclear receptor and then the receptor complex binds to DNAto produce mRNA
What are the effects of thyroid?
- stimulate __________ and ___________
- increase in _________ uptake
- mobilisation of endogenous ___________, ___________ and ____________
- produce more _________
- increase in ____________ and ____________
it has metabolic effects such as to
- stimulate metabolism and growth
- increase in food uptake
- mobilisation of endogenous carbohydrate, protein and fat
- produce more CO2
- increase in thermogenesis and sweating
What are three diseases of the thyroid?
- iodine deficiency disorder (simple goitre)
- Grave’s disease
- Hashimoto’s disease
What causes simple goitre?
The thyroid gland is not able to make enough thyroid hormone because there is not enough iodine and so there is an increase in the secretion of TRH from the hypothalamus and TSH from the anterior pituitary gland to stimulate the thyroid to make more TH.
What is a distinct feature of simple goitre and why does this occur? What can we do to treat this disease?
Bulging neck due to the swelling of the thyroid gland. This is because there is continual stimulation of the thyroid from TSH. To treat this, we can take iodine in our diet
What is the effect of simple goitre?
It leads to lower metabolism, less heat produced, no energy, cold
What causes Grave’s disease?
This is an autoimmune disease where the antibodies attack the thyroid and bind to the TSH receptor and replace its function so that there is an increase in metabolic function
How can we treat Grave’s disease?
with drugs that inhibit TH to stop thyroid hormone function
What is a distinct feature of grave’s disease and why does this occur? What other symptoms are there?
Bulging eyes because the tissue behind the eye is similar to the TSH receptor and so the antibody leads to inflammation of this tissue.
There is also an increase in metabolic functions, weight loss and hyperactivity
Body weight regulation is very _________
precise
On average, a person gains how much weight per year?
250g
What controls body weight regulation?
the brain
How accurate is the brain at controlling body weight regulation?
very
it has an accuracy of 99.8%
How precise are food labels at counting calories?
not very
they are off by about 25% (whereas the brain is only off by 0.2%)
Are diets a good weight loss technique?
no
How has the average BMI changed overtime?
it has greatly increased
A BMI in which range is classed as obese?
more than 35
BMI in which range is classed as healthy?
18-25 or 20-25 depending on the source