what is the function of thyroid hormones?
increases metabolism
increases protein synthesis
necessary or growth of children
disorders of the thyroid are among the _______ and affect how much of the US population?
they are among the most common endocrinopathies
they affect 4-5% of the population
what is the difference between the structure of T3 and T4?
a single atom of iodine
between T3 and T4, which is more active and which is released at a higher quantity?
T3 is more active
T4 is released in higher quantity
which (T3 or T4) is converted into the other?
T4 is converted into T3 once it reaches the target tissues
what does calcitonin do?
opposite action of parathyroid hormone
does NOT increase levels of calcium and phosphorus in blood
inhibits activity of osteoclasts and stops bone reabsorption
describe the structure of the thyroid gland
tiny saclike structures called follicles - func units
each follicle is formed by simply cuboidal epithelium
where are thyroid hormone made and stored?
they are made in the simple cuboidal cells of the thyroid and stored in the lumen attached to thyroglobulin
what are the 3 forms of thyroid hormones in the bloodstream?
bound to thyroxine-binding globulin
T4 binding prealbumin and albumin
free, unbound form - the active form
what enzyme converts T4 into T3?
5’-iodinase
what is a second form that T4 can be converted into?
reverse T3
a physiologically inactive form
actions of thyroid hormones in relation to GROWTH
growth formation
bone maturation
actions of thyroid hormones in relation to CNS
maturation of the CNS
actions of thyroid hormones in relation to BMR
increased Na-K ATPase
increased O2 consumption
increased heat production
increased BMR
actions of thyroid hormones in relation to METABOLISM
increased glucose absorption
increased glycogenolysis
increased gluconeogenesis
increased lipolysis
increased protein synthesis and degradation
actions of thyroid hormones in relation to CARDIOVASCULAR
increased cardiac output
define glycogenolysis
breakdown of glycogen to glucose
define gluconeogenesis
making of glucose from other products like amino acids or fats
what is goiter?
swelling of neck resulting from enlargement of the thyroid gland
what are the causes of goiter?
graves disease
TSH secreting tumor
iodine deficiency
what is hyperthyroidism?
tissues are exposed to high levels of circulating thyroid hormones
what are the causes of hyperthyroidism?
graves - most common
adenoma of thyroid
excessive production of TSH by pituitary adenoma
how many people does graves disease affect?
0.5-1% of population under 40
what is graves disease and its triggering factors?
state of hyperthyroidism, goiter, opthalmopathy
excessive stimulation of thy gland by IgG antibodies
triggering factors:
often unknown
genetic - history, gender
environmental - stress, smoking