24.5 Flashcards
(19 cards)
The thyroid gland secretes ___ hormones to regulate metabolism and secretes ___ to regulate calcium levels.
Thyroid hormones
Calcitonin
Thyroid hormones are produced in the ___ of the thyroid gland.
Colloid
___ cells in the ___ spaces secrete calcitonin for calcium metabolism.
C cells in interstitial spaces
Colloid is a glycoprotein mix filled with ___.
Thyroglobulin
___ is a precursor to thyroid hormones.
Tyrosine
Free T3 and T4 produced in follicular cells diffuses into circulation because it is ___.
Lipophilic or hydrophobic
T3/T4 binds to plasma proteins including ___-___ globulin, ___ and transthyretin.
Thyroid-binding globulin
Albumin
Transthyretin
T4 is also called ___ and is a prohormone.
Thyroxine
The half-life of T_ is short compared to T_.
T3 is less than T4
What are the actions of thyroid hormones?
Increased basal metabolic rate and O2 consumption - calorigenic/heat producing effects
Modulation of metabolism
Sympathomimetic effects (by increasing sensitivity to catecholamines?) - increase HR and CO
ESSENTIAL for GH and IGFs actions
Thyroid hormones are ___ for the actions of GH and IGFs
PERMISSIVE
Goitres occur because of stimulation of the ___ receptor. ___ or ___ stimulates the production of TH AND growth of the thyroid gland itself.
TSH
TSH or TSIs of Grave’s disease! (BOTH activate the TSH receptor)
What are the physiological effects of hypothyroidism?
(Opposite of normal effects of TH.)
Decreased basal metabolic rate and O2 consumption, decreased energy and increased weight
Cold intolerance
Sympathetic effects, decreased HR
Central effects, decreased mentation and reflexes, fatigue
Decreased protein synthesis, accumulation of mucopolysaccharides under skin
What is the treatment for thyroid hormone replacement?
Thyroid hormone replacement or increase in dietary iodine intake.
A common cause of primary hyperthyroidism is ___ disease.
Grave’s disease
In Grave’s disease, there is production of ___-___ ___ that targets ___ receptors resulting in increased production of thyroid hormones AND increased growth of the thyroid gland. There is strong negative feedback to reduce endogenous TRH and TSH levels.
Thyroid-stimulating immunoglobulin TSH receptors (on the thyroid gland)
What are the physiological effects of hyperthyroidism?
Increased basal metabolic rate and O2 consumption
Heat intolerance
Weight loss
Increase in appetite
Muscle weakness
Increase in HR
Increase in alertness, irritability and hyperexcitability
In Grave’s disease there can be ___ (bulging of the eyes) do to retention of water by ___ behind the eyes
Exophthalmos
Carbohydrates
What is the treatment for hyperthyroidism?
Remove thyroid/tumour
Use radioactive iodine to destroy gland
Anti-thyroid drugs e.g. to block TH synthesis or conversion of T4 to T3
