The thyroid gland Flashcards
What type of gland is the thyroid gland?
A ductless alveolar gland
What type of cells are thyroid follicular?
Simple cuboidal
Sympathetic innervation of the thyroid gland ……. thyroid secretion
Stimulates
Goitre is formed as as a result of chronic stimulation by which hormone?
TSH
What are the acute actions of TSH hormones on the follicular cells?
Synthesis, storage and secretion of T3 and T4
Which has a longer half life? T3 or T4?
T4
T3 and T4 is degraded by the removal of iodine. Which organs does this take place?
Liver and kidney
What are the actions of thyroid hormones? (3)
1) Increase BMR 2) Stimulates most metabolic pathways 3) Promotes normal growth + development of tissues
What is the effect of thyroid hormones on the CV system? (1)
Increases cardiac output
What is the effect of thyroid hormones on the nervous system? (3)
1) Increased myelination of nerve fibres and development of neurones 2) Increased speed of reflexes 3) Increased mental activity
Hypothyroidism in youth leads to what condition?
Cretinism
What some signs and symptoms of hyperthyroidism?
Sweating loads, weight loss, tachycardia, increased appetite, nervousness, irritability, hyper-reflexive and exophthalmus
Does Grave’s disease lead to hyper- or hypo- thyroidism?
Hyperthyroidism
What condition am I describing? “Production of antibody that stimulates the TSH receptor on follicle cells”
Grave’s disease
Carbinazole is used to treat hyperthyroidism. How does this drug work?
It inhibits the incorporation of iodine into thyroglobulin
What are the signs and symptoms of hypothyroidism?
Cold intolerance, mild weight gain, bradycardia, constipation, mood swings, poor concentration, oedema
What are the two possible mechanisms of Hashimoto’s disease?
Destruction of thyroid follicles or production of antibody that blocks the TSH receptor on follicle cells
How would you treat Hashimoto’s disease?
Oral T4
Which hormone secreted more from the thyroid gland? T4 or T3?
T4
What is the name of the key enzyme associated with thyroid hormone synthesis?
Thyroid peroxidase
What are the roles of thyroid peroxidase? (3)
1) Oxidation of iodide to iodine 2) Addition of iodine to tyrosine acceptor residues on thyroglobulin 3) Coupling of MIT or DIT to generate thyroid hormones within the thyroglobulin molecule
What is a “free” hormone?
A free hormone is one that is not bound to plasma proteins
Is thyroid disease more prevalent in males or females?
Females
What is sick euthyroid syndrome?
It is used to describe sick in-patients who frequently have abnormal TFTs despite being euthyroid
What is the most common cause of goitre?
Lack of dietary iodine
Thyroid hormone is derived from ……
Tyrosine
What is the name of the TSH sensitive ion pump that uptakes iodide?
The iodide trap
What type of hormone is thyroid stimulating hormone?
A glycoprotein hormone
What is subclinical hyperthyroidism?
It is characterised by a low or undetectable concentration of serum TSH with low T3 or T4
In Grave’s disease there is increased T3 and T4 and decreased TSH. True or false?
True
What is the half life of T4?
5-7 days
