Thyroid Flashcards
What is the thyroid regulated by
The hypothalamus and pituitary gland
What is the thyroid made up of
Follicles (hollow spheres) filled with colloid (protein rich fluid)
What does the colloid of the thyroid do
Is the site of much of the process of making the hormones
What do the parafollicular C cells release
Calcitonin
What releases the thyroid releasing hormone
The hypothalamus in the brain
What does the thyroid releasing hormone do
Bonds to receptors in the pituitary gland causing it to release thyroid stimulating hormone regulating the thyroid
What does TSH cause
The follicular cells in the thyroid to synthesise and release T3 and T4
Done through upregulation of genes which code for proteins in the thyroid hormone synthesis pathway
How do thyroid hormones travel
In the blood bound to proteins
How do thyroid hormones get to their target
Through blood then diffuse into target cells act via intracellular receptors releasing a depressor form certain genes which can be transcribed and translated to protein
What are 4 proteins as a result of thyroid hormones effects
Growth and development
Macronutrient metabolism
Basal metabolic rate
Synergy with catecholamines
How does parathyroid hormone work
Increasing Ca2+ released from the bones
Decreasing Ca2+ excretion by increasing reabsorption in the kidneys
What type of feedback is the hypothalamic pituitary thyroid axis
Negative feedback loop
What does high T3 and T4 levels cause
Suppression of TSH production
What do high TSH levels cause
Suppression of TRH production
What do thyroid hormones require
Iodine to synthesis T3 and T4
What does the drug caebimazole do
Helps to interfere with someone who produces too much T3 and T4 hormones
What are the most common thyroid hormone in the blood
T4 as when they synthesise in a cell they loose an iodine resulting in turning into T3
What do thyroid hormones do in macronutrient metabolism
Increase breakdown of glycogen and formation of glucose
Increase formation of lipids and lipid breakdown to release fatty acids - energy
What do thyroid hormones do for the basal metabolic rate
Increase this increasing heat generated by increasing ATPase expression
What happens when there is a lack of thyroid hormones in childhood
Potentially result in short stature and mental impairment
Low energy
Over heating
Weight change
What can an underactive thyroid (hypothyroidism) result in
Tiredness, lack of energy, weight gain, depression, sensitivity to cold
Caused by immune system attacking thyroid - Hashimoto disease
What can an overactive thyroid (hyperthyroidism) result in
Nervousness, anxiety, difficulty sleeping, tiredness, weight loss, sensitivity to heat
Caused by Graves’ disease where antibody is produced that mimics TSH leading to overproduction or caused by medications
What cells synthesis T3 and T4
Epithelial cells of the follicles
What are 4 affects of the thyroid hormones
Growth and development
Macronutrient metabolism
Basal metabolic rate
Synergy with catecholamines
