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 HormoneAction Thyrotropin (TSH)T 4 and T 3 release from thyroid Luteinizing hormone (LH)Testosterone synthesis in Leydig cells Progesterone synthesis in corpus luteum Follicle-stimulatingSpermatogenesis in Sertoli cells hormone (FSH)Estradiol synthesis in ovary; ovum maturation AdrenocorticotropicCortisol synthesis in adrenal cortex hormone (ACTH)

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 T 3 and T 4

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 Cyclopentanoperhydro- phenanthrene nucleus Act on nuclear receptors

Steroid Biosynthesis Begin by forming  5 -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 SteroidHormone-producing HormoneStructureSignal CortisolAdrenal cortex ACTH AldosteroneAdrenal cortexAngiotensin II/III TestosteroneLeydig cellLH EstradiolOvarian follicleFSH ProgesteroneCorpus luteumLH 1,25(OH) 2 D 3 KidneyParathyroid hormone (PTH)

Adrenal Hyperplasia 21-hydroxylase deficiency Lack of cortisol and aldosterone Buildup of androgens Masculanization Treated with cortisol

Actions of Steroid Hormones HormoneTarget Tissue/Effects ProgesteroneUterine endometrium, mammary EstradiolFemale: gonadotropin secretion, uterine endometrium Male: inhibit testosterone synthesis TestosteroneMale: converted to dihydrotestosterone, Sertoli cells, secondary sex characteristics CortisolStress adaptation, elevate liver glycogen, suppress immune responses AldosteroneKidney, Na + reabsorption to raise blood pressure

Vitamin D Synthesis D 3 produced in skin Further hydroxy- lations to form active 1,25-(OH 2 )D

Control of Serum Calcium Levels PTH produced in response to low serum calcium Synthesis of 1,25-(OH 2 )D induced by PTH 1,25-(OH 2 )D responsive genes in intestinal epithelial

1,25-(OH 2 )D and PTH act together in response to low serum calcium High serum calcium calcium decreases PTH, inactive 24,25(OH 2 )D synthesized

Vitamin D Deficiency and Toxicity Deficiency Rickets Improper bone and cartilage formation Toxicity Hypercalcemia Calcification in tissues, soft bones