Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BioMed > Hypothalamic - Pituitary - THYROID > Flashcards

Hypothalamic - Pituitary - THYROID Flashcards

1
Q

Outline the overall thyroid axis

A

Hypothalamic hormone is TRH

Anterior Pituitary is TSH

Endocrine target is the Thyroid Gland which secretes thyroid hormones

Non-endocrine target is many tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the structure of the thyroid ?

A

> just below larynx

> on either side of the trachea

> 2 lobes

> connected by isthmus

> largest purely endocrine gland (20-25 grams)

** lateral to first 3-8 trachael wings **

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Diagram of the thyroid

A

Follicles take up I- from the blood & secrete it into the colloid

In the colloid, I- is oxidized & attached to a tyrosine residue on thyroglobulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Production of thyroid hormones

A

Thyroglobulin : made by the follicle cells, it is a long peptide chain located in colloid with lots of tyrosine side chains

Iodid (I-) : transported from blood to follicular cells by a sodium-iodide transporter then transported into colloid via pendrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two ways iodine attaches to thyroglobulin ?

A

1) attachment of 1 iodine on a tyrosine produces monoiodotyrosine (MIT)
2) attachment of 2 iodines produces diiodotyrosine (DIT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do you make thyroid hormones ?

A

Enzymes in colloid modify structures of MIT and DIT to make the hormones

> MIT + DIT = triiodothyronine (T3)

> DIT + DIT = tetraiodothyronine (T4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How long does T3 & T4 stay bound to thyroglobulin ?

A

until hydrolyzed by a small volume of colloid and then they are secreted into the blood

STIMULATED BY TSH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Summary of production of thyroid hormones

A

Step 1 : enzyme thyroid peroxide (TPO) removes an eledtron from I- to produce I

Step 2 : iodine kinds tyrosine residues to form MIT & DIT

Step 3 : condensation of MIT & DIT residues to form T3 & T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does the receptor binding of thyroid receptors work ?

A

1) T4 and carrier binding protein enters target cell
2) T4 is converted to T3 (biologically active form)
3) T3 uses binding proteins to enter nucleus
4) Hormone-receptor comples binds DNA
5) New mRNA is the product
6) Protein Synthesis occurs making new protein
7) Initiates thyroid hormone response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the transportation of thyroid hormones

A

>99% of thyroid hormones in blood circulation bound to a plasma carrier protein called thryroxine-binding globulin (TBG)

  • only free fractions of thyroid hormones biologically are active; therefore has to lose the carrier protein to produce effects in target cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is TRH secretion regulated ?

A
  • Pulsed secretion of TRH
  • young animals > old animals
  • stress/cold increase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Circadian rhythm of thyroid hormones in humans, secretion is highest between 10am & 2pm.. WHY?

A

acting on basal metabolic rate; resting rate of calorie expenditure

>in mice/rodents, circadian rhythm of thyroid hormones secretion is highest at night because they are nocturnal animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Physiological action of thyroid hormones

A
  • elevates basal metabolic rate
  • needed for normal gonadal development and function
  • needed for normal embryonic/fetal development, particularly for the development of the CNS

** thyroid hormone deficiency or excess may therefore have serious consequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Compare hypo- and hyperthyroidism

A

Hypothyroid :

abnormally low basal metabolic rate - weight gain

lethargy

Intolerance to cold

Hyperthyroid :

Increased basal metabolic rate - weight loss

muscular weakness

nervousness

protruding eyes (exophtalmos)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is cretinism ?

A

Congenital deficiency of thyroid hormones; usually due to materal HYPO-thyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do you treat Cretinism ?

A

Treatment with thyroxine (T4) soon after birth (before 1 month) has shwon to (almost) completely restore development of intelligence by age 5

17
Q

Thyroid Hormones: terminal brain differentiation

A

Thyroid Hormone-dependent development of the brain beings in utero - completed after birth

Dendritic and axonal growth, myelin formation and synapsis formation

Neuronal migration

Maternal THs first supply the needs of the embryo/fetus

18
Q

Causes of cretinism

A

May be due to innate maternal hypothyroidism

Diet deficient in iodine (this deficiency affects many people worldwide)

19
Q

The causes of hypothyroidism and hyperthyroidism

A
  • Insufficient dietary iodide
  • Thyroid gland defect
  • Impaired Thyroid Hormone Pathway
  • insufficient anterior pituitary TSH
  • insufficient hypothalamic TRH
  • mutant TSH or TRH receptors (genetic)
  • mutant TH transport proteins
  • autoimmunity
20
Q

Goiters & HYPOthyroidism:

Abnormal Growth of Thyroid

A

Low iodide intake = thyroid cant produce enough thyroid hormones

Clinical signal: low plasma, thyroid hormones, T3, T4

High TRH

High plasma TSH

Stimulates excess growth of thyroid

21
Q

Graves & HYPERthyroidism

A

AutoAbs activate thyroid gland

Clinical signal: High plasma, thyroid, T3, T4

Low TRH

Low plasma TSH

22
Q

Synthetic thyroid medicine and natural thyroid medicine

A

Synthroid : Levothyroxine = T4

Natural : made from porcine thyroid

23
Q

Thyroid problems in animals

A

HYPERthyroid is common in cats

HYPOthyroid is more common in dogs

24
Q

Primary hypothyroidism (animals)

A

Most primary hypothyroidism in dogs is from destruction of the thyroid

Common causes, primary:

1) Lymphocytic thyroiditis (immune infiltration)

2) Idiopathic atrophy of the thyroid (thyroid lost and replaced by adipose cells)

25
Q

Secondary Hypothyroidism (animals)

A

Common causes, secondary:

1) thyroid destruction secondary to neoplasia

2) congenital hypothyroidism/cretinism/pituitary dwaarf

more than 75% of both lobes must be non-function before development of clinical signs: Myxedema (swelling of tissues) (severe HYPOthyroidism)/stupor/coma

26
Q

Treatment for thyroid disorders

A

1) Surgery (hemithyroidectomy)

2) Hormone supplementation (start with low doses)

3) Radiation Therapy (cancer)

4) Blockers (thiouracil derivatives - thiocarbamindes decrease iodionation and conversionof T4 into T3)

5) stimulants (furosemide; increase in conversion of T4 to T3)

6) Diet, electrolyte infusions, etc..

** TREATMENT ME BE FOR LIFE **

BioMed (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions