TRH, TSH, AND THYROID HORMONES

Question 1

Thyroxine (T4)

Answer 1

– 3,5,3’5’

Question 2

■ Triiodothyronine (T3)

Answer 2

– 3,5,3’

Question 3

■ reverse Triiodothronine (rT3)

Answer 3

– 3,3’,5’

Question 4

T4
– 100% of circulating is of thyroidal origin
– Half life:

Answer 4

8 days

Question 5

T4
– 70% -

– 20% -

– 10% -

– 0.04% are

Answer 5

Thyroxine/Thyroid-binding Globulin (TBG)

Transthyretin (TBPA)

Albumin (Thyroid-Binding Albumin)

unbound or free

Question 6

■ T3
– ______of circulating is of thyroidal origin
– ______ is produced enzymatically in
nonthyroidal tissues by
5’monodeiodination (via the enzyme
iodothyronine 5’-deiodinase) of T4 in the
liver and kidney

Answer 6

20%

80%

Question 7

T3
– Mostly is bound to_____
– Can be transported by ____
– 0.4% are unbound or free

Answer 7

TBG (Thyroxine-Binding Globulin)

TBG (Thyroxine-Binding Globulin)

Question 8

reverse T3 (rT3)
–______ major circulating form
– catalyzed by______
– no biological activity
– short half-life of_____
– circulates bound to____

Answer 8

third

5-deiodinase

4 hours

TBG

Question 9

is a modified tripeptide hormone produced in the hypothalamus.

Answer 9

Thyrotropin-releasing hormone (TRH)

Question 10

Thyrotropin Releasing Hormone
■ Modified tripeptide

Answer 10

pyroglutamyl-histidyl-proline-amide

Question 11

Thyroid-Stimulating Hormone
■ Glycoprotein with 2 monocovalently linked alpha and beta subunits
■_______
– same amino acid sequences as LH, FSH, and hCG
■_______
– carries specific information to the binding receptors for expression of hormonal activities

Answer 11

Alpha subunit

Beta - subunit

Question 12

Thyroid hormones are____ soluble

Answer 12

lipid

Question 13

■ Many of the actions of thyroid hormones are mediated by their binding to________ receptors that have a preferential affinity for____

Answer 13

nuclear

T3

Question 14

Thyroid hormone receptors exist in the
_______, not the cytoplasm, and may remain bound to DNA in the absence of hormone binding

Answer 14

nucleus of target cells

Question 15

Metabolism
■ Regulates of_________

■ Increases oxygen consumption in most target tissues

■ Permissive actions: TH increases sensitivity of target tissues to catecholamines, thereby elevating (3-LGG)

Answer 15

Basal Metabolic Rate (BMR)

lipolysis, glycogenolysis, and
gluconeogenesis

Question 16

Development

■ is critical for normal development of the (2)

■ essential for normal brain development and regulates (4)

Answer 16

skeletal system and musculature.

synaptogenesis
neuronal integration
myelination
cell migration

Question 17

Thyroid Hormone Function

Answer 17

■ Tissue growth
■ Development of the CNS
■ Elevated heat production
■ Energy conservation
■ Control of O2 consumption
■ Influence carbohydrate and protein
metabolism