Thyroid

Question 1

TRH from the hypothalamus stimulates ___ secretion from the anterior pituitary gland

(control of thyroid hormone secretion)

Answer 1

TSH

Question 2

Thyroid hormone synthesis/secretion occurs within the thyroid gland in the presence of __

(control of thyroid hormone secretion)

Answer 2

TSH

Question 3

Negative feedback causes the hypothalamus to stop or slow production of TRH which then causes the ___ pituitary to stop or slow release of TSH

Answer 3

anterior

Question 4

thyroid hormones, think:

Answer 4

T3, T4

Question 5

Anything that increases cellular energy demand causes an increase in __ production (e.g., Cold environment, hypoglycemia, high altitude, pregnancy
)

Answer 5

T3/T4

Question 6

Lateral lobes (wings) on each side of the trachea projecting upward to just below the ___

Lobes connected by an ___ located anterior to the trachea

(thyroid location)

Answer 6

larynx

isthmus

Question 7

Largest of pure endocrine glands

Answer 7

Thyroid gland

Question 8

A thyroid has an ___ blood supply

Answer 8

extensive

fer all them hormones

Question 9

___ are the functional units of the thyroid

Answer 9

Follicles

Question 10

A follicle is a sphere with its wall consisting of __ cells

Answer 10

follicular

Question 11

This inside of this unit is called the __

thyroid micro

Answer 11

colloid

Question 12

___ cells reside in between follicles

Answer 12

Parafollicular

produce calcitonin but not considered a thyroid hormone

Question 13

The inactive form of thyroid hormone

Much more abundant, but less potent

Answer 13

Tetraiodothyronine (Thyroxine, T4)

Question 14

The active form of thyroid hormone

Much more potent, less abundant

Answer 14

Triiodothyronine (T3)

Question 15

Made in small quantities by parafollicular cells, helps to regulate calcium levels of the blood

(not a “thyroid hormone” only made in the thyroid)

Answer 15

Calcitonin

Question 16

Follicular cells pull ___ ions from the blood stream

Answer 16

iodide

Question 17

Follicular cells are also producing ____

Answer 17

thyroglobulin (TGB) (glycoprotein-carbon chain of many amino acids)

Question 18

produced in endoplasmic reticulum

Packaged in the Golgi apparatus

Released by exocytosis into the lumen (colloid)

Answer 18

thyroglobulin (TGB)

glycoprotein-carbon chain of many amino acids – tyrosine

Question 19

Iodide requires ___ to make iodine (the useable form for thyroid hormone synthesis)

____ oxidizes the iodide into iodine (I2)

Answer 19

oxidation

Perioxidase

Question 20

(Insuffienct ___ lead to thyroid issues)

Answer 20

tyrosine, iodine, or peroxidase

Question 21

(T3 and T4 are __ soluble)

Answer 21

lipid

Question 22

At this point there is now TGB and iodine (I2) roaming in the colloid

Simultaneously TGB and ___ begin to react with each other forming bonds (at the tyrosine portions of TGB)

“middle step”

Answer 22

iodine

Question 23

One iodine to one tyrosine

Answer 23

monoiodotyrosine (MIT)

Question 24

Two iodines to one tyrosine

Answer 24

diiodotyrosine (DIT)

Question 25

These MIT and DIT molecules continue to form bonds to one another

Answer 25

MIT + DIT = T3 (3 iodine molecules)

DIT + DIT = T4 (4 iodine molecules)

Question 26

The colloid is then pulled back into the follicular cells by ___

Answer 26

pinocytosis

This colloid contains the T3 and T4

Question 27

Once back in the follicular cell, this colloid is engulfed by a lysosome which digests the TGB and cleaves off the ___

Answer 27

T3 and T4

Question 28

This T3 and T4 is sent out of the cell, into the interstitial space, into the bloodstream

Answer 28

Because they are weak in terms of water solubility, more than 99% of both T3 and T4 are then bound to transport proteins (thyroxine-binding globulin; TBG) in the blood stream

Question 29

This is the “glue” binding the MIT, DIT, T3, T4

Answer 29

TGB – Thyroglobulin

Question 30

This is the transport protein found in the blood stream that carries the T3/T4 to their target cells after synthesis of them is complete

Answer 30

TBG Thyroxine Binding Globulin

Question 31

Actions of Thyroid Hormones (T3/T4)

Answer 31

Increase basal metabolic rate (BMR)

Stimulates synthesis of additional Na+/K+ pumps

Helps to regulate the metabolism

Can enhance actions of some catecholamines

Works with hGH and insulin to accelerate body growth

Question 32

BMR is the rate of oxygen consumption under normal conditions

When increased, BMR causes metabolism of carbohydrates, proteins, and lipids

(Actions of Thyroid Hormones (T3/T4))

Answer 32

Increase basal metabolic rate (BMR)

Question 33

This causes increased ATP production and consumption by the constant turnover of the Na+ and K+

These reactions release heat as a byproduct

This heat helps to raise and maintain the body temperature

Answer 33

Stimulates synthesis of additional Na+/K+ pumps

Question 34

Stimulates protein synthesis

Increases use of glucose and fatty acid for ATP
production

Increases lipolysis and enhances cholesterol excretion

Answer 34

Helps to regulate the metabolism

Question 35

T3 and T4 upregulate ____ in the presence of these substances

Answer 35

beta adrenergic receptors

The upregulation can explain why hyperthyroid patients experience increased heart rates, and blood pressure

Question 36

____ of T3/T4 in fetal growth, infancy or childhood causes severe mental retardation and stunted bone growth

Answer 36

Deficiency