Thyroid Pt 1

Question 1

• The largest of the endocrine glands, the thyroid is located in the anterior neck directly below the larynx
• Shaped like a butterfly, the thyroid gland is highly vascular w/2 lobes, 1 on either side of the trachea joined by a small band of tissue called the isthmus

Answer 1

• The gland is firmly fixed by fibrous tissue to the anterior & lateral parts of the larynx & trachea
• Not normally visible on inspection, the thyroid gland is palpable during swallowing when it’s upwardly displaced

Question 2

Thyroid gland
- Thyroxine (T4)
- Triiodothyronine (T3)
- Calcitonin

Question 3

___ accounts for 90% of thyroid hormone produced by the thyroid gland

Answer 3

Thyroxine (T4)

Question 4

However, ___ is much more potent & has greater metabolic effects

Answer 4

triiodothyronine (T3)

Question 5

T4 & T3 affect

• metabolic rate
• caloric requirements
• oxygen consumption
• carb & lipid metabolism
• growth & development
• brain function & other nervous system activities

Question 6

Thyroid hormone production & release is stimulated by ___ from the anterior pituitary gland

Answer 6

TSH

Question 7

When circulating levels of thyroid hormone are low, the hypothalamus releases ___, which in turn causes the anterior pituitary to release TSH

Answer 7

TRH (thyrotropin-releasing hormone)

Question 8

High circulating thyroid hormone levels inhibit the secretion of both TRH from the hypothalamus & TSH from the anterior pituitary gland

Question 9

___ is produced by the thyroid gland in response to high circulating calcium levels

Answer 9

Calcitonin

Question 10

Calcitonin

• Inhibits the transfer of calcium from bone to blood
• Increases calcium storage in bone
• Increases renal excretion of calcium & phosphorus, thereby lowering serum calcium levels

Question 11

___ and ___ regulate calcium balance

Answer 11

calcitonin; PTH

Question 12

The parathyroid glands secrete ___, also called ___

! major role is to regulate blood level of calcium

Answer 12

PTH aka parathormone

Question 13

___ stimulates the transfer of calcium from the bone into the blood & inhibits bone formation, resulting in increased serum calcium & phosphate release from bone

Answer 13

PTH

Question 14

• In the kidney, PTH increases calcium reabsorption & phosphate excretion
• In addition, PTH stimulates the renal conversion of vitamin D to its most active form (1,25-dihydroxyvitamin D3)
• This active vit D promotes the absorption of calcium & phosphorus by the GI tract that ultimately increases bone mineralization

Answer 14

The secretion of PTH is directly regulated by a feedback system
- When the serum calcium level is low, PTH secretion increases

• When the serum calcium level rises, PTH secretion falls

Question 15

Functions of Thyroid Hormone

✓ Control basal metabolic rate of cells
✓ Regulates protein, carb, & fat metabolism
✓ Promotes growth hormone & gonadotropins, fetal
✓ Affects respiratory rate & drive

Answer 15

✓ Insulin antagonist
✓ Increases bone formation
✓ Direct effect on cardiac system
✓ Increase RBC production

Question 16

Classification of Disorders

1° thyroid dysfunction = problems w/the ___

Answer 16

thyroid

Question 17

2° thyroid dysfunction = problems w/the ___

Answer 17

pituitary

Question 18

3° thyroid dysfunction = problems @ the lvl of the ___

Answer 18

hypothalamus

Question 19

Problem(s) w/the hypothalamus & pituitary is also known as central

Question 20

Continuum of Thyroid Dysfunction