Thyroid Flashcards by Iseoluwa Ojo

Thyroid gland

located (above or below) the larynx on both sides and (anterior or posterior ?) to the trachea

2 lobes joined by an _____
normal adult weight is __-___g

Below
Anterior

isthmus

15-20

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Thyroid gland is minimally vascularized

T/F

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Thyroid gland is made up of numerous _____

follicles

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follicles are ____ in shape and lined by (single or double?) layer of cuboidal epithelium

-follicles are filled with ____

spherical

Single

colloid

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follicular cells synthesize _____ and ____

thyroxine and T3

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colloid is mainly made up of the (small or large?) ______ called ______ that is synthesized and secreted by the ____ and _____

Large

glycoprotein

thyroglobulin

ER wnd golgi complex

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thyroglobulin has a molecular weight of ______ and contains —— _____amino acids

660000

140 tyrosine

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SYNTHESIS OF THYROID HORMONE

_____ is essential for synthesis of thyroid hormones
minimum daily intake in food and water is ___-___mg

iodine

100-150

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iodine is converted to ____ in gut and absorbed into blood and ECF

iodide

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about _/3 of absorbed iodide is taken up by the thyroid while _/3 is excreted by the kidneys

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STEPS INVOLVED IN THYROID HORMONE SYNTHESIS

synthesis of _____ and its extrusion into the _____ from the ___ membrane
_____ to pump iodine into the cell from the ____ membrane
oxidation of iodine to ____(I to I2)

thyroglobulin

follicular Lumen

apical

iodide pump

basal

iodide

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STEPS INVOLVED IN THYROID HORMONE SYNTHESIS

After oxidizing iodine to iodide

organization of iodide into ___ and _____

coupling reaction of ___ and ___ into ___ and ____
__cystosis of ___

MIT and DIT

MIT and DIT; T3 and T4

exo ; TG

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STEPS INVOLVED IN THYROID HORMONE SYNTHESIS

After taking TG coupled with T4 and T3 back into the cell from the apical membrane

____ of T4 and T3, T4 and T3 enters the circulation
-____ of the remaining MIT and DIT. ___ and ___ is recirculated

hydrolysis

deiodination

Iodide and tyrosine

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Organification of thyroglobulin

-binding of _____ with _____ in the thyroglobulin

iodine with amino acid

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TG is released from the cell into the blood from the basal membrane

T/F

TH itself isn’t released

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RELEASE of TG

-______ are cleaved from the TG molecule and released into the blood

T4 and T3

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TRANSPORT of TG

__% bind with tyrosine-binding ___
__% bind with tyrosine binding ___
___% with serum ___
less than ___% in free form

67; globulin

20; prealbumin(TBPA)

13; albumin

0.1

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In the transport of T4 , ____ has the greatest affinity to bind T4

TBG

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In the binding of T4, ____ has the smallest capacity to bind T4

TBG

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_____ has the largest capacity to bind T4

albumin

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SECRETION of TG

normal human thyroid secretes about : *__mg of T4/day
__mg of T3/day
__mg of RT3/ day

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Control of Secretion of TG

TSH ___eases TH secretion
T4’s feedback at ____ or ____ levels control TSH release
cold (stimulates or reduces?) TSH
warmth (stimulates or reduces?) TSH
stress (stimulates or reduces?) TSH
glucocorticoids (excite or inhibit?) TRH

incr

pituitary; hypothalamic

stimulates

reduces

Reduces

Inhibit

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Stimulatory Factors of thyroid hormone

TSH
thyroid _____
increased level of TBG (eg In _____)

stimulating immunoglobulins

pregnancy

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perchlorate and thiocynate inhibits _____

iodide pump

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iodide deficiency inhibits T4 production deiodinase deficiency stimulates T4 production Low iodide intake inhibits T4 production low levels of TBG stimulates T4 production T/F

T F F F

low levels of TBG can be caused by liver diseases T/F

proprothiouracil inhibits _____ enzyme

peroxidase

FUNCTIONS of thyroid hormones - (activates or inhibits?) nuclear transcription of genes - ___eases Na-k atpase - ___ease number and activity of mitochondria - promote Brain growth during ___ life and ____ years of post natal life

Activates incr fetal first few

Specific functions of thyroid hormones (A) Carbohydrate metabolism - (slow or rapid?)uptake of glucose by cells - ___eases gluconeogenesis - ___eases rate of absorption from GIT - ___eases insulin secretion

Rapid incr incr incr

Thyroid hormones aid glycolysis | T/F

Specific functions of thyroid hormones Fat Metabolism - __eases mobilization of lipid from fat tissue - ___elerates the oxidation of free fatty acids by the cells

incr acc

Specific functions of thyroid hormones Vitamin Metabolism -demand for vitamins is ____eased leading to increased vitamin deficiency

incr

Thyroid hormone increases BMR T/F

Specific functions of thyroid hormones CVS - ___eased blood flow leading to ___eased cardiac output - __eased heart rate due to (direct or indirect?) effect on its excitability - ___eased strength of heart muscle

incr incr incr;direct incr

Thyroid hormone effect on heart muscle strength(increasing it) is depressed with marked increase in thyroid hormone T/F

Specific functions of thyroid hormones respiration -___ease rate and depth of respiration

incr

Specific functions of thyroid hormones GIT - ______ appetite leading to _____ food intake - ____ eased secretion of digestive juices - ____eased gastric motility that can lead to ____ is in excess

enhanced increased incr incr diarrhea

Specific functions of thyroid hormones CNS -excess causes extreme ____ and ____ and ____

nervousness anxiety Worry

Specific functions of thyroid hormones Muscles - slight ____ in thyroid hormones leads to the hormone reacting with vigor - muscle becomes ____ due to ____ protein catabolism

increase weakened excess

Specific functions of thyroid hormones Sleep -(easy or difficult?) to sleep

difficult

Specific functions of thyroid hormones other endocrine glands - ___eases the rate of secretion of most other endocrine glands

increases

Excess thyroid hormone can cause fine muscle tremor | T/F

Specific functions of thyroid hormones effect on sexual function -in men, lack of thyroid hormone leads to ____ of libido and excess can lead to _____ - in women, lack of thyroid hormones lead to __________ ,_____ period and occasionally ____ - excess in women causes ______ and ______

loss impotence excessive and frequent menstrual bleeding irregular; amenorrhea greatly reduced bleeding and amenorrhea

Infantile form of hypothyroidism is _____ * adult form of hypothyroidism is _____ * hypersecretion of Thyroid hormone causes _____ or ______

cretinism myxedema grave’s disease toxic goiter

Grave’s disease | -characterized by _____ circulating levels of TSI

increased

Grave’s disease is an autoimmune disorder | T/F

In grave’s disease TSI are _____ to TSH receptors on thyroid follicular cells And when present , the TSI intensely ____ the thyroid gland resulting in __eased secretion of thyroid hormone and ___trophy of the gland

antibodies Stimulate incr hyper

The follicular epithelial cells are arranged in circular follicles ____ µm in diameter

200– 300

_______ converts T4 to T3

5′-iodinase

Thyroid hormone secretion is in a pulsatile manner T/F

F It’s steady

Obesity increases the conversion of T4 to rT3 T/F

F To T3

pregnancy decrease the conversion of T4 to T3 | T/F

fasting increase the conversion of T4 to T3 | T/F

F Decr

stress increase the conversion of T4 to T3 | T/F

F Decreas

hepatic and renal failure decrease the conversion of T4 to T3 T/F

Thyroid hormones increase oxygen consumption in all tissues except ____,____,____

brain, gonads, and spleen

Thyroid hormones increase both protein synthesis and degradation, but overall their effect is _____

catabolic

In adults, hypothyroidism causes ____ness, (rapid or slowed?) movement, somnolence, (intact or impaired?) memory, and ___eased mental capacity. Hyperthyroidism causes ____excitability, _____reflexia, and irritability.

listless slowed impaired Decr Hyper; hyper

if the cause of hyperthyroidism is increased secretion of TRH or TSH then TSH levels will be ____eased.

Incr

Treatment of hypothyroidism involves thyroid hormone replacement therapy, usually T__

r. TSH-secreting tumors are an (common or uncommon?) cause of hyperthyroidism.

Uncommon

Autoimmune thyroiditis is a common cause of hypothyroidism, in which thyroid hormone synthesis is impaired by _____ to _____, leading to decreased T4 and T3 secretion.

antibodies peroxidase

Autoimmune thyroiditis causes goiter T/F