The document describes several endocrine glands and their hormones. It discusses the thyroid gland, which produces thyroxine (T4) and triiodothyronine (T3) to regulate metabolism. The parathyroid glands secrete parathyroid hormone to regulate blood calcium levels. The adrenal glands are composed of an outer cortex that produces corticosteroids like cortisol and aldosterone, and an inner medulla that secretes epinephrine and norepinephrine. The pancreas contains islets of Langerhans that secrete insulin and glucagon to regulate blood sugar levels.

2. Hormones of the Posterior Pituitary
Slide 9.22
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 Oxytocin
Stimulates contractions of the uterus during
labor
Causes milk ejection
 Antidiuretic hormone (ADH)
Can inhibit urine production
In large amounts, causes vasoconstriction
leading to increased blood pressure
(vasopressin)

3. Hormones of the Posterior Pituitary
Slide 9.22b
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Figure 9.5

4. Thyroid Gland
Slide 9.23a
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 Found at the base of the throat
 Consists of two lobes and a connecting
isthmus
 Produces two hormones
Thyroid hormone
Calcitonin

5. Thyroid Gland
Slide 9.23b
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Figure 9.6

6. Thyroid Hormone
Slide 9.24
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 Major metabolic hormone
 Composed of two active iodine-
containing hormones
Thyroxine (T4) – secreted by thyroid
follicles
Triiodothyronine (T3) – conversion of T4 at
target tissues

7. Calcitonin
Slide 9.25
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 Decreases blood
calcium levels by
causing its
deposition on bone
 Antagonistic to
parathyroid
hormone
 Produced by C
(parafollicular)
cells
Figure 9.9

8. Parathyroid Glands
Slide 9.26
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 Tiny masses on the posterior of the
thyroid
 Secrete parathyroid hormone
Stimulate osterclasts to remove calcium
from bone
Stimulate the kidneys and intestine to
absorb more calcium
Raise calcium levels in the blood

9. Thyroid Gland
• The largest
endocrine gland,
located in the
anterior neck,
consists of two
lateral lobes
connected by a
median tissue mass
called the isthmus
• Composed of
follicles that
produce the Figure 17.8a

10. Thyroid Gland
• Colloid
(thyroglobulin +
iodine) fills the
lumen of the
follicles and is the
precursor of thyroid
hormone
• Other endocrine
cells, the
parafollicular cells,
produce the
hormone calcitonin
Figure 17.8a

11. Thyroid Hormone (TH)
• Thyroid hormone – the body’s major metabolic
hormone
• Consists of two closely-related iodine-containing
compounds
• T4 – thyroxine; has two tyrosine molecules plus four
bound iodine atoms
• T3 – triiodothyronine; has two tyrosines with three
bound iodine atoms

12. Effects of Thyroid Hormone
• TH is concerned with:
• Glucose oxidation
• Increasing metabolic rate
• Heat production
• TH plays a role in:
• Maintaining blood pressure
• Regulating tissue growth
• Developing skeletal and nervous systems
• Maturation and reproductive capabilities

13. Transport and Regulation of TH
• T4 and T3 bind to thyroxine-binding globulins
(TBGs) produced by the liver
• Both bind to target receptors, but T3 is ten times
more active than T4
• Peripheral tissues convert T4 to T3
• Mechanisms of activity are similar to steroids
• Regulation is by negative feedback
• Hypothalamic thyrotropin-releasing hormone
(TRH) can overcome the negative feedback

14. Synthesis of Thyroid Hormone
• Thyroglobulin is synthesized and discharged into
the lumen
• Iodides (I–) are actively taken into the cell, oxidized
to iodine (I2), and released into the lumen
• Iodine attaches to tyrosine, mediated by peroxidase
enzymes, forming T1 (monoiodotyrosine, or MIT),
and T2 (diiodotyrosine, or DIT)
• Iodinated tyrosines link together to form T3 and T4
• Colloid is then endocytosed and combined with a
lysosome, where T3 and T4 are cleaved and diffuse

15. Synthesis of Thyroid Hormone
Figure 17.9

16. Calcitonin
• A peptide hormone produced by the parafollicular,
or C, cells
• Lowers blood calcium levels in children
• Antagonist to parathyroid hormone (PTH)
• Calcitonin targets the skeleton, where it:
• Inhibits osteoclast activity and thus bone resorption and
release of calcium from the bone matrix
• Stimulates calcium uptake and incorporation into the
bone matrix
• Regulated by a humoral (calcium ion concentration

17. Parathyroid Glands
• Tiny glands
embedded in the
posterior aspect of
the thyroid
• Cells are arranged in
cords containing
oxyphil and chief
cells
• Chief (principal) cells
secrete PTH
• PTH (parathormone)
Figure 17.10a

18. Effects of Parathyroid Hormone
• PTH release increases Ca2+
in the blood as it:
• Stimulates osteoclasts to
digest bone matrix
• Enhances the reabsorption
of Ca2+ and the secretion of
phosphate by the kidneys
• Increases absorption of Ca2+
by intestinal mucosal cells
• Rising Ca2+ in the blood
inhibits PTH release
Figure 17.11

19. Adrenal (Suprarenal) Glands
• Adrenal glands – paired, pyramid-shaped organs
atop the kidneys
• Structurally and functionally, they are two glands
in one
• Adrenal medulla – nervous tissue that acts as part of the
SNS
• Adrenal cortex – glandular tissue derived from
embryonic mesoderm

20. Adrenal Cortex
• Synthesizes and releases steroid hormones called
corticosteroids
• Different corticosteriods are produced in each of
the three layers
• Zona glomerulosa – mineralocorticoids (chiefly
aldosterone)
• Zona fasciculata – glucocorticoids (chiefly cortisol)
• Zona reticularis – gonadocorticoids (chiefly androgens)

21. Adrenal Cortex
Figure 17.12

22. Adrenal Glands
Slide 9.27
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 Two glands
Cortex – outer glandular region in three
layers
Medulla – inner neural tissue region
 Sits on top of the kidneys

23. Hormones of the Adrenal Cortex
Slide 9.28a
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 Mineralocorticoids (mainly aldosterone)
Produced in outer adrenal cortex
Regulate mineral content in blood, water,
and electrolyte balance
Target organ is the kidney
Production stimulated by renin and
aldosterone
Production inhibited by atrial natriuretic
peptide

24. Hormones of the Adrenal Cortex
Slide 9.28b
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Figure 9.10

25. Hormones of the Adrenal Cortex
Slide 9.29a
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 Glucocorticoids (including cortisone and
cortisol)
Produced in the middle layer of the adrenal
cortex
Promote normal cell metabolism
Help resist long-term stressors
Released in response to increased blood
levels of ACTH

26. Hormones of the Adrenal Cortex
Slide 9.29b
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 Sex hormones
Produced in the inner layer of the adrenal
cortex
Androgens (male) and some estrogen
(female)

27. Hormones of the Adrenal Medulla
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 Produces two similar hormones
(catecholamines)
Epinephrine
Norepinephrine
 These hormones prepare the body to
deal with short-term stress

28. Pancreatic Islets
Slide 9.32a
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 The pancreas is a mixed gland
 The islets of the pancreas produce
hormones
Insulin – allows glucose to cross plasma
membranes into cells from beta cells
Glucagon – allows glucose to enter the
blood from alpha cells
These hormones are antagonists that
maintain blood sugar homeostasis

29. Pancreatic Islets
Slide 9.32b
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Figure 9.13

30. Pancreatic Hormones and Blood Sugar
Slide 9.33
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Figure 9.14

31. Pineal Gland
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 Found on the third ventricle of the brain
 Secretes melatonin
Helps establish the body’s wake and sleep
cycles
May have other as-yet-unsubstantiated
functions

32. Thymus
Slide 9.35
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 Located posterior to the sternum
 Largest in infants and children
 Produces thymosin
Matures some types of white blood cells
Important in developing the immune system

33. Hormones of the Ovaries
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 Estrogens
 Produced by Graafian follicles or the placenta
 Stimulates the development of secondary
female characteristics
 Matures female reproductive organs
 Helps prepare the uterus to receive a fertilized
egg
 Helps maintain pregnancy
 Prepares the breasts to produce milk

34. Hormones of the Ovaries
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 Progesterone
Produced by the corpus luteum
Acts with estrogen to bring about the
menstrual cycle
Helps in the implantation of an embryo in
the uterus

35. Hormones of the Testes
Slide 9.38
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 Interstitial cells of testes are hormone-
producing
 Produce several androgens
 Testosterone is the most important
androgen
Responsible for adult male secondary sex
characteristics
Promotes growth and maturation of male
reproductive system
Required for sperm cell production

36. Other Hormone-Producing Tissues
and Organs
Slide 9.39
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 Parts of the small intestine
 Parts of the stomach
 Kidneys
 Heart
 Many other areas have scattered
endocrine cells

37. Endocrine Function of the Placenta
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 Produces hormones that maintain the
pregnancy
 Some hormones play a part in the
delivery of the baby
 Produces HCG in addition to estrogen,
progesterone, and other hormones

38. Developmental Aspects of the
Endocrine System
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 Most endocrine organs operate smoothly
until old age
 Menopause is brought about by lack of
efficiency of the ovaries
 Problems associated with reduced estrogen
are common
 Growth hormone production declines with age
 Many endocrine glands decrease output with
age