T1 L7 :Thyroid Hormone Physiology Flashcards
what is the thyroid gland composed off in terms of cells
Follicles
What is colloid
A reservoir of thyroid hormone
what is the name of T3 and T4
T3= triiodothyronine
T4=
Tetraiodothyronine
(thyroxine )
What does Di and monoiodotyrosine combine to form (MIT and DIT)
Forms T3 and T4
where is iodine derived from
Plants
What is T4 converted into in the tissues
T3
what can Fe deficiency cause
It can disrupt iodine absorption leading to dysfunction of the thyroid gland
what can radioactive iodine cause
Deficiency of iodine absorption in the thyroid gland (as radioactive iodine absorbed kills of the thyroid glands cells)
what is the thyroid hormone made up of predominately?
T4
hat is the active form of the thyroid hormone
T3
what form of the thyroid hormone is given as medication
T4
what converts T4 to T3
Deiodinase enzymes
what other product is produced from T4
reverse T3
is reverse T3 active ?
No it’s inactive
what causes the secretion of the thyroid hormone (from a centre in the brain)
Hypothalamus- TRH
Pituitary -TSH
Thyroid gland - T3 and T4
what is the negative feedback of T3/4 release
The inhibition of TSH (and assume therefore the inhibition of TRH)
what cause Derbyshire neck
A loss of I2 causes an increase in the release of TSH which causes hypertrophy of the thyroid gland
what metabolic effects does the thyroid hormone cause (3 effects)
Carbohydrate metabolism
Protein synthesis
Lipolysis
what does thyroid hormone cause in the foetus
It causes the myelination of the nerve fibres
how is albumin transported in the blood
10% albumin
20% TBPA(thyroxine-binding prealbumin)
75% T4 bound to thyronine-binding globulin
what occurs when thyroxine travels across cells
Binds to intracellular receptors at the nucleus and influences gene transcription and thus protein synthesis
what happens after gene transcription
More mitochondria and increased activity
what are the effects of an increased carbohydrate metabolism
- glycogenesis and glucose uptake by muscle cells and adipose cells
- potentiation of the effects of insulin
- potentiation of the effects of the catecholamines
- increase in glucose absorption by the gastrointestinal tract.
Which organs does the thyroid hormone not cause an increase in metabolism for
Brain Uterus Testes Spleen Thyroid gland Anterior pituitary gland
You can live as an adult without your thyroid gland but u need it as a kid,
If so
what are thyroid hormones essential for
Normal growth
development
what does a decrease in iodine cause or humans
Puberty inhibition so you don’t grow and always remain looking like a child
CORE DRUG: LEVOTHYROXINE
Its used to treat thyroid deficiency
Suppresses TSH secretion and can be given by mouth or injection
overdoes: Palpitations and arrhythmias
Lithium does what to the thyroid hormone
It inhibits its secretion
CORE DRUG : What does propylthiouracil do to the thyroid gland
prevents the peripheral conversion of T4 to T3.
which normally acts in thyroid hormone synthesis. PTU also acts by inhibiting tetraiodothyronine deiodinase which converts T4 to T3. Drug of choice to treat hyperthyroidism in first trimester
CAUSES- pruritus
what does K+ perchlorate do
Potassium perchlorate acts by competing with iodide for the active iodide uptake pump.
CORE DRUG :what does Carbimazole (methimazole) do
act by inhibition of the synthesis of thyroid hormones by preventing the incorporation of the iodide into the thyroglobulin.
which prevents peroxidase iodinating the tyrosine residues on thyroglobulin, hence reducing the production of the thyroid hormones T3 and T4.
can cause Pruritus
what drugs can reduce goitre and how do they work
Lithium
Iodides
These ions are selectively concentrated within the thyroid gland where they interfere with iodide incorporation and hormone release.
what is an alternate to using carbimazole in pregnant women and why
Propylthiouracil: it has a short half life and so its better than carbimazole for breastfeeding mothers
