Thyroid Gland

Question 1

Describe the structure and location of the thyroid gland.

Answer 1

Two lobes connected by a narrow thyroid tissue called isthmus

The front of the neck below Adam’s apple

Question 2

Identify the types of cells within the thyroid gland that produce hormones.

Answer 2

Follicular cells

Parafollicular cells (C cells)

Question 3

Compare and contrast T4 and T3.

Answer 3

Both:
- Has multiple ions
Found in the thyroid gland

T4 (Thyroxine):
- Four iodide ions
- makes up about 90 percent of circulating thyroid hormone
- Most is converted to T3 by target tissues.

T3 (Triiodothyronine):
- Three iodide ions
- More powerful than T4
- Makes up about 10 percent of circulation thyroid hormone

Question 4

How do T4 and T3 affect body cells?

Answer 4

Increases metabolism that causes cells to absorb more carbohydrates, use more energy, and produce more heat

Question 5

Explain how T4 and T3 production is regulated.

Answer 5

By a negative feedback loop.

When levels are too high, hypothalamus stops making TRH, which also stops the anterior gland to stop making TSH.

When levels are two low, hypothalamus secretes TRH, which causes the anterior pituitary gland to secrete TSH.

Question 6

What is the function of calcitonin?

Answer 6

Regulate blood calcium levels by stimulating the movement of calcium into bone

Question 7

Identify the chief cause and effects of hyperthyroidism.

Answer 7

Thyroid gland produces too much thyroid hormones

Question 8

What are two possible causes of hypothyroidism?

Answer 8

Surgical removal of the thyroid

Dietary iodine deficiency

Question 9

List signs and symptoms of hypothyroidism.

Answer 9

Thyroid gland growing in size and producing a goiter

Slow heart rate

Carpal tunnel syndrome

Weight gain with poor appetite.

Question 10

Why may both hyperthyroidism and hypothyroidism cause goiters?

Answer 10

Goiters from hyperthyroidism:
Thyroid glands wanting to maintain an equal amount of space for the increasing output of hormones.

Goiters from hypothyroidism:
Negative feedback loop of repeated stimulation of the thyroid, despite the fact that the necessary hormones cannot be produced

Question 11

Choose one symptom each for hyperthyroidism and hypothyroidism and explain why they occur based on the functions of thyroid hormones.

Answer 11

Hyperthyroidism:
Weight loss with increased appetite
- Excess of thyroid hormones increase cellular metabolism

Hypothyroidism:
Weight gain with decreased appetite
- Lack of thyroid hormones slows the body’s metabolism

Question 12

Which hormone is produced by the thyroid gland?
A. T3
B. Calcitonin
C. Parathyroid hormone
D. TSH
E. A and B

Answer 12

E. A and B
T3 and Calcitonin

Question 13

In cases of hypothyroidism due to Hashimoto’s thyroiditis or removal of the thyroid gland to treat hyperthyroidism, patients are often given medication to replace the missing thyroid hormone. Explain why the level of replacement thyroid hormone must be carefully monitored and adjusted if needed.

Answer 13

Because there is no accurate feedback loop that can accurately control the level of thyroid hormones anymore, it must be monitored externally.

Question 14

rue or False. T3 and T4 bind to receptors on the plasma membrane of target cells.

Answer 14

False

Question 15

Which disease causes too much thyroid hormone to be produced?
A. Hashimoto’s thyroiditis
B. Graves’ disease
C. Goiter
D. Iodine deficiency

Answer 15

B. Graves’ disease