1. Unit Fourteen: Endocrinology and Reproduction
Chapter 75: Pituitary Hormones and Their
Control by the Hypothalamus
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. Pituitary Gland and Its Relation to the Hypothalamus
Pituitary Gland Has Two Distinct Parts
Anterior pituitary (adenohypophysis)
Posterior pituitary (neurohypophysis)
Between the two is the pars intermedia

3. Pituitary Gland and Its Relation to the Hypothalamus
Pituitary Gland Has Two Distinct Parts
Fig Pituitary gland

4. Pituitary Gland and Its Relation to the Hypothalamus
Anterior pituitary produces 6 important peptide
hormones (and several of lesser importance)
Posterior pituitary secretes two important peptide
hormones (produced in the hypothalamus)

5. Pituitary Gland and Its Relation to the Hypothalamus
Fig Metabolic functions of the anterior pituitary hormones.
ACH, adrenal corticosteroid hormones

6. Pituitary Gland and Its Relation to the Hypothalamus
Control of Metabolic Functions (Anterior Pituitary)
Growth hormone-promotes growth of the entire body
affecting protein formation, cell growth, and cell
differentiation
Adrenocorticotropin-controls the secretion of some of
the adrenocorticotropical hormones, which affect the
metabolism of glucose, proteins, and fats
Prolactin-promotes mammary gland development
and milk production

7. Pituitary Gland and Its Relation to the Hypothalamus
Control of Metabolic Functions (Anterior Pituitary)
Thyroid stimulating hormone-controls the rate of
secretion of thyroxine and T3 which controls the rates of
most intracellular chemical reactions
Follicle stimulating hormone and leutinizing hormone-
control the growth of the ovaries and testes, as well as
their hormonal and reproductive activities

8. Pituitary Gland and Its Relation to the Hypothalamus
Control of Metabolic Functions (Posterior Pituitary)
Antidiuretic hormone (vasopressin)-controls the rate
of water excretion in the urine
oxytocin-helps express milk from the mammary glands
during suckling and helps in the delivery of the baby

9. Pituitary Gland and Its Relation to the Hypothalamus
Anterior Pituitary Gland Contains Different Cell
Types That Synthesize and Secrete Hormones
Somatotropes-human growth hormone
Corticotropes-ACTH
Thyrotropes-TSH
Gonadotropes-LH and FSH
Lactotropes-PRL

10. Pituitary Gland and Its Relation to the Hypothalamus
Hypothalamus Controls Pituitary Secretion
Posterior pituitary-controlled by nerve signals that
originate in the hypothalamus
Anterior pituitary-controlled by hormones called
hypothalamic releasing or hypothalamic inhibiting
hormones

11. Hypothalamus Controls Pituitary Secretion
Fig Hypothalamic-hypophyseal portal system

12. Hypothalamus Controls Pituitary Secretion
Hypothalamic-Hypophysial Portal Blood Vessels
of the Anterior Pituitary Gland
Small arteries penetrate the median eminence, and
additional vessels return to the surface coalescing
to form the portal system
These vessels pass downward along the pituitary
stalk to supply blood to the anterior pituitary
sinuses

13. Hypothalamus Controls Pituitary Secretion
Hypothalamic Releasing and Inhibitory Hormones
are Secreted into the Median Eminence
The endings of the neurons are special in that their
function is not to transmit signals from one neuron
to another but rather to secrete the hormones
The hormones are absorbed into the portal system
and carried directly to the anterior pituitary

14. Hypothalamus Controls Pituitary Secretion
Hypothalamic Releasing and Inhibitory Hormones
Control Anterior Pituitary Secretion
Thyrotropin releasing hormone (TRH)
Corticotropin releasing hormone (CRH)
Growth hormone releasing hormone (GHRH)
Gonadotropin releasing hormone (GnRH)
Prolactin inhibitory hormone (PIH)

15. Physiological Functions of Growth Hormone
Growth Hormone Promotes Growth of Many
Body Tissues
GH is also called somatotropin and is a single chain
of 191 amino acids
Causes growth of almost all tissues
Promotes increased sizes of cells and increased
mitosis
Promotes the greater development of cells and
specific differentiation

16. Physiological Functions of Growth Hormone
Growth Hormone Promotes Growth of Many
Body Tissues
Fig Comparison of weight gain of a rat injected daily with GH
with that of a normal littermate

17. Physiological Functions of Growth Hormone
Growth Hormone Metabolic Effects
Promotes protein deposition in tissues
Enhancement of aa transport through the cell
membranes
Enhancement of RNA translation to cause
protein synthesis by the ribosomes
Increased nuclear transcription of nuclear DNA
to form RNA
4) Decreased catabolism of protein and amino acids

18. Physiological Functions of Growth Hormone
Growth Hormone Metabolic Effects
b. GH enhances fat utilization for energy
Causes the release of fatty acids from adipose
Enhances the conversion of fatty acids to
acetyl coA
3) If too great a release, then ketosis can occur

19. Physiological Functions of Growth Hormone
Growth Hormone Metabolic Effects
c. GH decreases carbohydrate utilization
Decreased glucose uptake in tissues such as
skeletal muscle and fat
Increased glucose production by the liver
Increased insulin secretion

20. Physiological Functions of Growth Hormone
Growth Hormone Metabolic Effects
d. GH stimulates cartilage and bone growth
Increased deposition of protein chondrocytes and
osteoprogenitor cells
Increased rate of reproduction of these cells
A specific effect of converting chondrocytes into
osteogenic cells
Strongly stimulates osteoblasts in the periosteum
and cavities
5) Effects bone bone growth in length and width

21. Physiological Functions of Growth Hormone
Growth Hormone Metabolic Effects
GH exerts much of its effects through intermediates
called somatomedins or insulin-like growth factors

22. Physiological Functions of Growth Hormone
Regulation of Growth Hormone Secretion
Stimulate GH Secretion
Inhibit GH Secretion
Decreased blood glucose
Increased blood glucose
Decreased blood free fatty acids
Increased blood free fatty acids
Increased blood amino acids (Arg)
Aging
Starvation, fasting, protein deficiency
Obesity
Trauma, stress, excitement
GHIH (somatostatin)
Exercise
Growth hormone (exogenous)
Testosterone, estrogen
Somatomedins (insulin-like growth factors)
Deep sleep (stages II and IV)
GHRH
Ghrelin

23. Physiological Functions of Growth Hormone
Abnormalities of GH Secretion
Dwarfism
Giantism
Acromegaly

24. Posterior Pituitary and Its Relation to the Hypothalamus
Pituicytes- glial like cells that make up the posterior
pituitary
Pituicytes do not secrete hormones but act as
supporting structures for terminal nerve fibers and
nerve endings
Nerve fibers and endings contain bulbous knobs
that contain secretory granules which release two
hormones—oxytocin and vasopressin (ADH)
The two hormones originate in two different nuclei
of the hypothalamus

25. Posterior Pituitary and Its Relation to the Hypothalamus
Fig Hypothalamic control of the posterior pituitary

26. Posterior Pituitary and Its Relation to the Hypothalamus
Physiological Functions of Antidiuretic Hormone
In the presence of ADH the permeability of the
collecting ducts and tubules of the kidney to water
increases greatly and allows water to be reabsorbed,
conserving water in the body and producing very
concentrated urine
Mechanism is probably by increased insertion of
aquaporins in the membranes (cAMP mediated)

27. Posterior Pituitary and Its Relation to the Hypothalamus
Regulation of ADH Production
Increased ECF osmolarity stimulates ADH secretion
Low blood volume and low blood pressure
stimulate ADH secretion (called the vasoconstrictor
effects of ADH)

28. Posterior Pituitary and Its Relation to the Hypothalamus
Oxytocic Hormone
Causes contraction of the pregnant uterus
Aids in milk ejection by the breasts