Transcript Hormonal Cascade System

Hormonal Cascade System
Connection of
hypothalamus and pituitary
• Hypothalamus to anterior
pituitary to ultimate glands
– Releasing hormones
– Amplification of signal
– Negative feedback
• Posterior pituitary
Some Major Hormones of
Anterior Pituitary
Hormone
Action
Thyrotropin (TSH)
T4 and T3 release from thyroid
Luteinizing hormone (LH)
Testosterone synthesis in Leydig cells
Progesterone synthesis in corpus luteum
Follicle-stimulating
hormone (FSH)
Spermatogenesis in Sertoli cells
Estradiol synthesis in ovary; ovum maturation
Adrenocorticotropic
hormone (ACTH)
Cortisol synthesis in adrenal cortex
Synthesis of Peptide Hormones
• Proopiomelanocortin is precursor
polypeptide for eight hormones
• Other genes encode only one hormone
Thyroid Hormone
• Iodination of
tyrosine residues in
thyroglobulin
• Proteolysis releases
T3 and T4
Epinephrine
• Adrenal medulla
• Derived from tyrosine
or phenylalanine
• Targets hepatocytes
and vascular smooth
muscle cells
• Begin with tyrosine or
phenylalanine; hydroxylations
• Norepinephrine converted to
epinephrine by PNMT
Neuronal and glucocorticoid
regulation
Steroid Hormones
• Adrenal cortex, ovary
and testes
• Derived from cholesterol
• Cyclopentanoperhydrophenanthrene nucleus
• Act on nuclear receptors
Steroid Biosynthesis
• Begin by forming D5-pregnenolone
• Further modifications for specific steroids
• Involves cytochrome P450's
Control of Steroid Synthesis
• Cell surface receptor activated
• Stimulate conversion of cholesterol
Hormones that Stimulate
Synthesis of Steroid Hormones
Steroid
Hormone
Hormone-producing
Structure
Signal
Cortisol
Adrenal cortex
ACTH
Aldosterone
Adrenal cortex
Angiotensin II/III
Testosterone
Leydig cell
LH
Estradiol
Ovarian follicle
FSH
Progesterone
Corpus luteum
LH
1,25(OH)2 D3
Kidney
Parathyroid hormone (PTH)
Adrenal Hyperplasia
•
•
•
•
•
21-hydroxylase deficiency
Lack of cortisol and aldosterone
Buildup of androgens
Masculanization
Treated with cortisol
Actions of Steroid Hormones
Hormone
Target Tissue/Effects
Progesterone
Uterine endometrium, mammary
Estradiol
Female: gonadotropin secretion, uterine endometrium
Male: inhibit testosterone synthesis
Testosterone
Male: converted to dihydrotestosterone, Sertoli cells,
secondary sex characteristics
Cortisol
Stress adaptation, elevate liver glycogen, suppress
immune responses
Aldosterone
Kidney, Na+ reabsorption to raise blood pressure
Vitamin D Synthesis
• D3 produced in skin
• Further hydroxylations to form active
1,25-(OH2)D
Control of Serum Calcium Levels
• PTH produced in response
to low serum calcium
• Synthesis of 1,25-(OH2)D
induced by PTH
• 1,25-(OH2)D responsive
genes in intestinal epithelial
• 1,25-(OH2)D and PTH
act together in response
to low serum calcium
• High serum calcium
calcium decreases PTH,
inactive 24,25(OH2)D
synthesized
Vitamin D Deficiency and
Toxicity
Deficiency
• Rickets
• Improper bone and cartilage formation
Toxicity
• Hypercalcemia
• Calcification in tissues, soft bones