endocrine 4 - thyroid Flashcards
what do the thyroid follicles secrete
T3 and T4
what do the parafollicular cells secrete
calcitonin
what is the difference with the resting and the active follicle
active is enlarged and more plump, the central area is smaller but still filled with colloid
what amino acid and element are needed to make thyroid hormones
tyrosine and iodine
what are the intermediates to thyroid hormones
MIT and DIT
how is iodide taken into the cell
active transport by Na I pump
what is thyroglobulin
glycoprotein that contains tyrosine
what makes MIT
tyr + 1 iodine
what makes DIT
tyr + 2 iodine
what makes T3
MIT + DIT
what makes T4
DIT + DIT
how does TSH enhance thyroid hormone synthesis
increase Na I pump and increase thyroglobulin synthesis (first 2 steps)
what happens to T4 and T3 once they are made in the colloid
they are endocyzed from the lumen back into the cell
how are T3 and T4 released from thyroglobulin
lysosomal enzymes
what happens once T3 and T4 are released from thyroglobulin
they are secreted into the blood, I- and amino acids recycles
which thyroid hormone is secreted more into the blood
T4>T3
how is T3 and T4 transported in the blood
bound to thyroid binding protein
which T is more potent
T3
T4 is a prohormone
what happens to T4
it is converted into T3 in peripheral cells and liver
where does T3 bind
nuclear receptors (fat soluble)
what percent is T4 and T3 made
90% T4
10% T3
which thyroid hormone is a prohormone
T4
what stimulates TSH
TRH
where is TRH from
hypothalamus
where is TSH from
pituitary
what stimulates T3 and T4 production
TSH
what negatively inhibits TSH
T4 and T3
what negatively inhibits TRH
T4 and T3
how do thyroid hormones act on most tissues
change transcription and translation
what do thyroid hormones do to metabolism
increase
what is thyroid hormone role in growth
it is required for growth and development
what does thyroid hormone do to basal metabolic rate
increase
what does thyroid hormone do to 02 consumption
increase
what does thyroid hormone do to heat production
increase
what does thyroid hormone do to catabolism and what causes this
increase (too much T3)
what does thyroid hormone do to anabolism and what causes this
increase (some T3)
what does thyroid hormone do to carbohydrate absorption
increase
what does thyroid hormone do to carbohydrate utilization
increase
what does thyroid hormone do to protein breakdown
increase
what does thyroid hormone do to fat breakdown (lipolysis)?
increase
what does thyroid hormone do to cholesterol metabolism
increase
what does thyroid hormone do to serum cholesterol
decrease
how much thyroid hormone do to protein synthesis
small amounts
how do thyroid hormones act as for growth and development
as tissue growth factors
what does thyroid hormone do to GH/IGF1 production
increase (GH causes IGF1 production in liver)
what does thyroid hormone do to CNS maturation in fetus
essential, increase
what happens with maternal hypothyroidism to the fetus
poor fetal CNS development and mental retardation
what does thyroid hormone do to heart rate
increase
what does thyroid hormone do to heart contractility
increase
what does thyroid hormone do to BP
increase
what does thyroid hormone do to sympathetic nervous system
potentiate beta2 adrenergic receptors
what does thyroid hormone do to women reproduction system
necessary for normal function and fertility
what is Graves disease (simple definition)
overactivity of the thyroid gland
what kind of disorder causes graves disease
autoimmune
explain how graves disease works
antibodies to the TSH receptor stimulates thyroid hormone preoduction
what happens to basal metabolic rate in graves disease
increase
what is exophthalmos
eyes popping out
what disease causes exothalmos
graves disease
what is hashimotos thyroiditis (simple definition)
underactive thyroid gland
what kind of disorder causes hashimotos thyroiditis
autoimmune
how does Hashimotos thyroiditis work
thyroid peroxidase (TPO) antibodies destroy thyroid gland to block hormone synthesis
what is cretinism
growth delay, small body, mental retardation in children
which disease causes cretinism in children
Hashimoto’s thyroiditis
what is myxedema
lethargy, like depression
which disease causes myxedema
Hashimoto’s thyroiditis
which disease causes goitre
Hashimoto’s thyroiditis and graves disease
which disease causes cold intolerance
hypothyroidism / Hashimoto’s thyroiditis
which disease causes weight gain
hypothyroidism / Hashimoto’s thyroiditis
which disease causes menorrhagia
hypothyroidism / Hashimoto’s thyroiditis
what is menorrhagia
profuse menstrual flow
how is goitre made in hyperthyroidism
thyroid stimulating immunoglobulins stimulate the thyroid gland to make the goitre
how is goitre made in hypothyroidism
low iodine in diet lowers T3 and T4 causing an increase in TSH which causes goitre (no iodine in diet, T4 and T3 remains low)
what is the best way to measure thyroid function
test TSH levels in blood
what is the most common cause of hypothyroidism, goitre, mental retardation and preventible brain damage?
iodine deficiency
is there low or high TSH in blood in hyperthyroidism
low
is there low or high TSH in blood in hypothyroidism
high