Thyroid Hormone Flashcards
What is the anatomy of the thyroid gland divided into?
clusters of follicles via connective tissues
What does a thyroid gland follicle consist of?
Thin layer of epithelial cells and colloid
What is the function of the epithelial cells?
they are responsible for the synthesis of thyroid hormones
What are four different ways that thyroid hormones can be transported?
99.5% binds to plasma proteins
TBG is a glycoprotein with a high affinity
TBPA is a protein with a low affinity
ALB/ albumin is a protein that also has a low affinity
How is thyroid hormone production regulated?
Hypothalamus produces TRH which then acts on the anterior pituitary to release TSH which is neccesary for the release of TH
What is the function of TH relating to metabolism?
It increases the overall basal metabolic rate, regulates the rate of O2 consumption and energy expenditure
What is the function of TH relating to neural function?
important during foetal life and early brain development/ myelination so it increases axonal speed conduction
What is the function of TH relating to the cardiovascular system?
It increases blood flow and cardiac output
How does TH effect thermogenesis
It increases heat production and oxygen consumption
How does TH effect carbohydrate metabolism?
Stimulates glycogenolysis in the liver
What effect does TH have on lipid metabolism?
It stimulates release of free fatty acids by increasing the activity of hormone sensitive lipase in adipocytes
What effect does TH have on protein metabolism?
It stimulates the synthesis of proteins mainly involved in oxidative reactions
What is hypothyroidism?
sub-optimal levels of TH
What is primary hypothyroidism?
relates to the thyroid gland itself, the plasma TH is still high
atrophy of the thyroid gland
What is secondary hypothyroidism?
It is related to the pituitary gland, the plasma TSH is low
What are some clinical signs of hypothyroidism?
mental retardation, slow metabolism, feeling cold, weight gain, sluggishness, skin issues
skin thickening/ myexdema
What is hyperthyroidism?
Excessive production of T3/T4, associated with a high metabolic rate
most common in cats
What kind of tumour is hyperthyroidism most commonly associated with?
a benign thyroid tumour
What are some clinical signs of hyperthyroidism
Increased body temperature, weight loss
Increased heart rate and work load
loss of skeletal mass
What is Exophthalmos?
complex water retaining carbs are maintained behind the eyes which pushes the eyes out
What is Goitre?
an enlarged thyroid gland
What causes goitre?
iodine deficiency, iodine toxicity, ingestion of certain plants
What is thyroglobulin?
Source of thyroid hormone
What effect will T3/T4 have on the production of TRH?
Long loop negative feedback
