physio- thyroid hormones

TRH (thyrotropin releasing hormone)

what does the hypothalamus release to the anterior pituitary in order to stimulate the thyroid gland?

TSH (thyroid stimulating hormone)

what does the anterior pituitary release to the thyroid gland stimulate the production of hormones?

TRH (thyrotropin releasing hormone)

what is 1?

TSH (thyroid stimulating hormone)

what is 2?

T3 and T4

what are 3 and 4?

next to the trachea

where is the thyroid gland located?

follicle cells

what part of the thyroid gland produces thyroglobulin (Tg)?

thyroglobulin (Tg)

what do the follicle cells in the thyroid gland produce?

triiodothyronine (T3)

tetraiodothyronine (T4)

calcitonin

what are the 3 hormones released by the thyroid gland?

tyrosine

T3 and T4 are derived from the modification of _____

amine hormones

what type of hormones are thyroid hormones (T3, T4, calcitonin)?

liposoluble

are thyroid hormones hydrosoluble or liposoluble?

hours

how long is the half life of thyroid hormones?

follicular cells

what cells in the thyroid gland synthesize, store, and release T3 and T4?

parafollicular cells

what cells in the thyroid gland synthesize, store, and release calcitonin?

with TBG (type of binding proteins)

also can be transported with albumin and prealbumin

how are thyroid hormones transported in the plasma?

metabolic regulation

thyroid hormones contribute to the __________ of all tissues during development

inside of the cell- on the nucleus (because they are liposoluble)

where are the receptors for thyroid hormones (on cell membrane or inside of the cell)?

T4

which, T3 or T4 is secreted more?

T4

which, T3 or T4, acts as a circulating prohormone?

T3

which, T3 or T4, exerts almost all hormonal activity in target cells?

tyrosine, iodine

what are the 2 molecules necessary for the synthesis of T3 and T4?

1. collection and concentration of iodide in thyroid gland

2. oxidation and incorporation of iodine to phenol ring of tyrosine

3. coupling of 2 molecule of iodine-tyrosine to form T3 or T4

what are the 3 steps in the synthesis of thyroid hormones?

thyroid cells capture iodide (first step of synthesis)

what is occurring here?

1. the iodide is oxidized to iodine by an enzyme

2. the cells synthesize thyroglobulin

3. iodine is added to thyroglobulin (specifically, the tyrosine residues of the thyroglobulin)

explain what is happening here, in the process of synthesizing thyroid hormones

it is oxidized, turning into iodine, and then added to the tyrosine residues of the thyroglobulin

in the synthesis of thyroid hormones, what happens to the iodide after it is captured by the follicular cells?

1 or 2

1- monoiodidotyrosine

2- diiodidotyrosine

how many iodines can be added to a tyrosine residue?

the tyrosine residues are linked together, making couples

in the synthesis of thyroid hormones, what happens after the iodine is added to the tyrosine residues of thyroglobulin?

iodine is added to the tyrosine residues of thyroglobulin

what step of thyroid hormone synthesis is this?

(after the iodine is added) the tyrosine residues are linked together, making couples

in the synthesis of thyroid hormones, what is occurring here?

hydrosoluble

are the immature coupled tyrosines hydrosoluble or liposolible?

secretion-

first, cells take up portions of thyroglobulin, and then once the protein is ruptured (hydrolized) because of TSH from the anterior pituitary, T3 and T4 become liposoluble and are released

in the synthesis of thyroid hormones, after the coupling of tyrosine, what occurs?

TSH (thyroid stimulating hormone)

what signals trigger the hydrolization of thyroglobulin, which ultimately causes the maturation of T3/T4?

it triggers the hydrolization of thyroglobulin, which causes the maturation of T3/T4- making them liposoluble and able to leave the cell

what exactly is the mechanism of TSH to the thyroid gland?

T3

(T4 has to convert into T3 before going to the nucleus)

which, T3 or T4, can go directly to the nucleus of the target cell?

deiodinase (it removes an iodine)

what enzyme converts T4 into T3?

gene expression is modified

once T3 is bound to the nucleus of the target cell, what is the result?

increased cell metabolism, increasing production of energy

what is the general effect of T3 and T4?

TBG (thyroid binding globulin)

prealbumin

albumin

what are the binding proteins that allow thyroid hormones to be transported in plasma?

less than 1%

what % of thyroid hormone circulates freely(before binding to a transporter)

T4

which, T3 or T4, has more affinity for binding proteins?

T4- because it is protected by TBG

which, T3 or T4, has a longer half-life?

T4

which, T3 or T4, is synthesized more?

T3- because it binds better to the receptors

which, T3 or T4, has more activity?

the free hormone (without binding protein)

what is the active form of the thyroid hormone?

TBG

which of the binding proteins, TBG, prealbumin, or albumin, is least concentrated in the blood (least amount)?

TBG

which of the binding proteins, TBG, prealbumin, or albumin, has the most binding strength?

albumin

which of the binding proteins, TBG, prealbumin, or albumin, has the weakest binding strength?

albumin

which of the binding proteins, TBG, prealbumin, or albumin, is the most concentrated in plasma (most amount)?

no

is there a large concentration of TBG in the blood?

bound to a transport protein (TBG, pre-albumin, albumin)

when the thyroid hormone is _______, it is inactive

liver and kidneys

where does deiodination of T4 (to convert it into T3) take place in the body?

reverse T3

when T4 is converted to T3, an equal amount of ______ is also formed

a form of T3 that does not work, made when metabolism does not need increasing

what is reverse T3, and why is it made?

short stature and mental deficits (cretinism)

the lack of thyroid hormones during development causes...

increases and stimulates it

what do thyroid hormones do to metabolism?

nervous system tissues

thyroid hormones are essential for the normal growth of tissues, especially __________

growth hormone and prolactin

thyroid hormones are necessary for the production and secretion of what other 2 hormones?

increases their glucose reabsorption

what effect do thyroid hormones have on intestines?

increase

what effect do thyroid hormones have on ATP production?

increases its production of adrenaline and noradrenaline

what effect do thyroid hormones have on the adrenal medulla?

increase

do thyroid hormones increase or decrease the production of adrenaline and noradrenaline?

increases protein degradation

what effect do thyroid hormones have on proteins?

catabolic effect- increases breakdown of glycogen into glucose to use for energy

what effect do thyroid hormones have on carbohydrates?

T3 increases the number of Na/K+ ATPase pumps, which increases ATP consumption

what effect do thyroid hormones have on the Na/K+ ATPase pumps?

makes the mitochondria produce more ATP- making more energy and heat

what effect do thyroid hormones have on mitochondria?

kidneys, liver, skeletal muscle

where are thyroid hormones degraded?

it decreases the production

how does an iodine deficiency effect thyroid hormones?

decrease (negative feedback)

an increase in thyroid hormones has what effect on TSH/TRH production?

hyperthyroidism and hypothyroidism

what 2 diseases are associated with thyroid problems?

hypothyroidism

which, hypothyroidism or hyperthyroidism is more common in dogs?

LOW metabolism

this causes:

less heat production

laziness, lethargy

skin issues

decreased appetite but increased weight

nonregenerative anemia

hyperlipidemia

what are the problems caused by hypothyroidism?

swollen thyroid gland

what is goitre?

because metabolism is so low, that the thyroid gland is overstimulated to work better

why does hypothyroidism cause goitre?

the baby will have cretinism, decreased mental and physical growth

what happens if a pregnant animal is hypothyroidic?

hypothyroidism

what disease do these animals have?

hyperthyroidism

what disease do these animals have?

hyperthyroidism

which endocrinopathy related to metabolism is more common in cats?

increased metabolism

this causes-

increased appetite but decreased weight

increased heat production

lots of urination and drinking

increased heartrate and cardiac output

increased red blood cells (erythrocytosis)

decreased/weak muscle

decreased cholesterol levels

nervousness, aggressiveness

what is caused by hyperthyroidism?

because the thyroid gland is working too hard

why does hyperthyroidism cause goitre?

hypothyroidism

which, hyperthyroidism or hypothyroidism, causes fatigue and laziness?

hyperthyroidism

which, hyperthyroidism or hypothyroidism, causes nervousness and aggressiveness?

hypothyroidism

which, hyperthyroidism or hypothyroidism, makes the animal fatter?

hyperthyroidism

which, hyperthyroidism or hypothyroidism, makes the animal lose weight?