Thyroid Gland

Question 1

Function & form of the Thyroid gland

Answer 1

Secretes three hormones

Two lobes connected by a narrow band of tissue called an isnthmus

Question 2

Thyroglobulin

Answer 2

A highly concentrated protein that is synthesized and secreted by cells of the thyroid follicle. It is the precursor to thyroid hormones and stores a huge amount of a thyroid hormone.

Question 3

Parafollicular cells

Answer 3

cells of the thyroid that lie between follicles.

Question 4

Calcitonin

Answer 4

Secreted by parafollicular cells

reduced concentration of calcium in body fluids when calcium levels are elevated

Question 5

Thyroid hormones

Answer 5

Triiodothyronine (T3)
Tetraiodothyronine
Thyroxine T4
Calcitonin

Question 6

What causes secretion and synthesis from the thyroid hormone?

Answer 6

TSH (thyroid stimulating hormone) from the anterior pituitary gland

Question 7

Response of T3 and T4

Answer 7

Increased metabolic rate
Increased protein synthesis
Essential for normal growth and maturation

Targets most cells of the body

Question 8

Why is iodine essential in human diets?

Answer 8

Iodine is an integral component of T3 and T4, so humans must consume enough to support thyroid hormone synthesis

Question 9

How are t3 and T4 transported through the blood?

Answer 9

Travel in combination with plasma proteins

75% are bound to thyroxine-binding globulin (TBG)

20-30% bound to other plasma proteins

Question 10

Why is the half life of T3 and T4 so long? ~1 week

Answer 10

There is so much circulating in plasma proteins

Question 11

How do T3 and T4 bind to target tissues?

Answer 11

They are lipid soluble, so they bind to nuclear receptors in target tissues

Question 12

what are the effects of t3 and t4?

Answer 12

Metabolism
Growth an maturation

Effect almost every tissue in the body, but affect it differently.

Question 13

Effects of hypothyroidism

Answer 13

decrease metabolism, weight gain, reduced appetite, apathy, myxedema, reduced heart rate, weak muscles,

Question 14

Effects of hypertheroidism

Answer 14

increased metabolism, high body temp, weight loss, increased appetite, copious sweating, rapid heart rate, weak skeletal muscles, diarrhea, hyperactivity, irritability,

Question 15

Which two hormones regulate Thyroid hormone secretion?

Answer 15

Thyrotropin-releasing hormone (TRH) from hypothalamus

TSH from anterior pitutiary

Question 16

Calcitonin

Answer 16

target tissue is bone.

Decreases osteoclast activity, lengthen life span of osteoblasts

Question 17

Goiter

Answer 17

Abnormal englargement of the thyroid gland.

Result from either hypothyroidism or hypertheyroidism

Question 18

Iodine-deficiency goiter

Answer 18

When dietary iodine intake is so low that the body can’t synthesize T3 and T4, blood levels of T3 and T4 decrease, and person exhibits symptoms of hypothyroidism

Question 19

Toxic goiter

Answer 19

Secretes excess T3 and T4

Symptoms are hyperthyroidism

Question 20

Exophthalmos

Answer 20

Protruding eyes, a symptom of hyperthyroidism.

Not easily reversed, even if thyroid gland removed.