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ENDOCRINE SYSTEM
Chapter 16
ENDOCRINE GLANDS
Ductless glands that produce hormones that
are released directly into the bloodstream
and are transported throughout the body to
regulate the metabolic function of other
cells in the body.
Types of hormones:
Paracrine
 Autocrine
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Chemical Nature of Hormones
Amino-acid based hormones
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Amines=simple hormones derived from tyrosine
(example: Epinephrine)
Protein and peptides=chains of amino acids hooked
together (example: ADH or Oxytocin)
Steroid-based hormones
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Progesterone
Testosterone
Eicosanoids
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Hormone-like substances that act only on cells in the
immediate vicinity (example: prostaglandin)
Functions of Hormones
Integrative
Homeostatic
Growth
Mechanisms of Hormone Action
Lipid-soluble hormones
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Diffusion occurs
Binds to intracellular
receptors
Forms hormone-receptor
complexes
Hormone-receptor complex
binds to specific receptor
proteins on DNA
Initiates transcription of
certain genes
Mechanisms of Hormone Action
Cyclic AMP signaling
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Hormone binds to cell
membrane receptor
Hormone-receptor complex
binds to inactive G protein
G protein becomes active by
GTP to GDP
G protein binds adenylate
cyclase producing Cyclic
AMP
Cyclic AMP activates
protein kinase enzymes
Mechanisms of Hormone Action
PIP-calcium signaling
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Hormone binds to cell
membrane receptor
Hormone-receptor
complex binds to inactive
G protein
G protein becomes active
and binds to phospholipase
Phospholipase splits to
form IP3 and DAG which
activate protein kinases
and calcium
Control of Hormones
Feedback Mechanisms
Negative feedback
 Positive feedback
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Responsiveness to target cells
Concentrations of hormones
 Number of receptors
 Interaction of other hormones
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Control of Hormones
Major Endocrine Glands
Pituitary Gland
Thyroid Gland
Parathyroid Gland
Adrenal Gland
Thymus Gland
Pineal Gland
Other endocrine tissue
Pituitary Gland (Hypophysis)
Posterior lobe
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Oxytocin
ADH
Anterior lobe
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GH
TSH
ACTH
FSH
LH
PRL
MSH
Thyroid Gland
Follicles and follicle cells
Thyroglobulin
Colloid
Thyroxine (T4)
Triiodothyronine (T3)
Calorigenic effect
Calcitonin produced by
parafollicular cells
Parathyroid Gland
Produces parathyroid
hormone (PTH)
Regulates calcium
levels by targeting:
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Bones
Intestine
Kidneys
Adrenal Gland
Adrenal Cortex
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Zona glomerulosa
produces
mineralcorticoids
Zona fasciculate
produces
glucocorticoids
Zona reticularis
produces androgens
or adrenal sex
hormones
Adrenal Gland (continued)
Adrenal Medulla
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Chromaffin cells
Epinephrine
Norepinephrine
Associated with stress
or “Fight or Flight”
responses
Thymus and Pineal Gland
Thymus Gland
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Thymosin stimulates
T-cell maturation
Immune system
Pineal Gland
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Pinealocytes
Melatonin
Pancreas
Alpha Cells
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Produce glucagon
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Glycogen>>Glugacon>>Glucose
Beta Cells
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Produce insulin
Enhances uptake of glucose by cells
as well as inhibits glycogenolysis
and gluconeogenesis
Delta Cells
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Somatostatin
Acinar Cells
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Produces pancreatic enzymes but
are exocrine
Pancreas (continued)
Other Endocrine Tissues
Ovaries=produce estrogen and progesterone
Testes=produce testosterone and inhibin
Placenta=produces HCG
Heart=secretes ANP
Kidneys=secrete erythropoietin
Skin=produces choleocalciferol
Adipose tissue=releases leptin
Gastrointestinal tract=releases gastrin, secretin,
serotonin, cholecystokinin and others
Homeostatic Imbalances
Gigantism
Acromegaly
Progeria
Pituitary dwarfism
Galactorrhea
Gynecomastia
Myxedema
Goiter
Cretinism
Grave’s disease
Hyperparathyroidism
Hypoparathyroidism
Diabetes insipidus
Diabetes mellitus
Aldosteronism
Addison’s disease
Cushing’s disease
Masculinization
Thyroid Gland (continued)
Thyroid Gland (continued)
Cushing’s Disease
Cushing’ Disease
Acromegaly
Gigantism and Pituitary Dwarfism
Addison’s Disease