1. The Endocrine System Thyroid & Parathyroid

2. Thyroid Gland Found at the base of the throat
Consists of two lobes and a connecting isthmus
Produces two hormones
Thyroid hormone
Calcitonin

3. Thyroid Gland Thyroid hormone Major metabolic hormone
Composed of two active iodine-containing hormones
Thyroxine (T4) —secreted by thyroid follicles
Triiodothyronine (T3) —conversion of T4 at target tissues

4. Thyroid Gland Thyroid hormone disorders Goiters
Thyroid gland enlarges due to lack of iodine
Salt is iodized to prevent goiters

5. Thyroid Gland Thyroid hormone disorders Cretinism
Caused by hyposecretion of thyroxine
Results in dwarfism during childhood

6. Thyroid Gland Thyroid hormone disorders (continued) Myxedema
Caused by hypothyroidism in adults
Results in physical and mental sluggishness

7. Thyroid Gland Thyroid hormone disorders (continued) Graves’ disease
Caused by hyperthyroidism
Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos

8. Thyroid Gland Calcitonin
Decreases blood calcium levels by causing its deposition on bone
Antagonistic to parathyroid hormone
Produced by parafollicular cells
Parafollicular cells are found between the follicles

9. Parathyroid Glands Tiny masses on the posterior of the thyroid
Secrete parathyroid hormone (PTH)
Stimulate osteoclasts to remove calcium from bone
Stimulate the kidneys and intestine to absorb more calcium
Raise calcium levels in the blood

10. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood Ca2+
levels
Thyroid gland releases calcitonin
Osteoclasts degrade bone matrix and release Ca2+ into blood
PTH
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood Ca2+ levels
Imbalance
Figure 9.10

11. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Imbalance
Figure 9.10, step 1

12. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland
Imbalance
Figure 9.10, step 2

13. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland releases calcitonin
Calcitonin
Thyroid gland
Imbalance
Figure 9.10, step 3

14. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland releases calcitonin
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Thyroid gland
Imbalance
Figure 9.10, step 4

15. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland releases calcitonin
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Thyroid gland
Figure 9.10, step 5

16. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 6

17. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Thyroid gland
Parathyroid glands
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 7

18. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
PTH
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 8

19. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Osteoclasts
degrade bone matrix and release Ca2+ into blood
PTH
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 9

20. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Osteoclasts
degrade bone matrix and release Ca2+ into blood
PTH
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Figure 9.10, step 10

21. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood Ca2+
levels
Thyroid gland releases calcitonin
Osteoclasts degrade bone matrix and release Ca2+ into blood
PTH
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood Ca2+ levels
Imbalance
Figure 9.10, step 11