Bio117 Chapter 7: Endocrine System

Hormones

Organic (not carbon dioxide)

Living Cells (not chemicals from dead cells)

Localized (not glucose needed in every cell)

Distance (not neurotransmitters)

Target Cells with Specific Receptors (not nutrients)

Exocrine Glands

Sweat glands, oil glands, tear ducts

Endocrine Glands

Hypothalamus, thyroid glands, pituitary gland, adrenal glands, pancreas

Endocrine System

collection of endocrine glands throughout the body that secrets hormones into the blood stream to alter the body’s physiology to help maintain homeostasis.

Parts of Endocrine System

Hypothalamus, anterior pituitary, thyroid, thymus, liver, adrenal medulla, adrenal cortex, kidneys, intestines, pineal (epiphysis), posterior pituitary, parathyroid glands, heart, stomach, pancreas, ovaries, uterus, placenta, testes

Eicosanoids

Unusual story, “local hormone”, derives from membrane phospholipids, can act on many levels: 2nd messengers, autocrine, paracrine, hormone

Growth Factors (GF)

Unusual story, can be hormones, cytokines, and paracrines, often influence cell cycle checkpoints

GF Examples

Epidermal GF, Ovarian GF, FDGF (Fibroblast-derived), IGF (insulin-like GF)

Oncogenes

cancer-linked genes, associated with GF-associated genes

Oncogene Products

include altered versions of: affected GF, GF receptor, and protein downstream (chain of communication)

APUD

Amine Precursor Uptake Decarboxylation

APUDomas

Unusual story, tumor of APUD cells, Ectopic secretion (secretion in the wrong location), secrete biogenic amines, protein or peptide hormones are often co-secreted with amines

APUDoma Example

Men can sometimes have tumors(APUDomas) in the lungs that produce hCG (Chronic Gonadotropin hormone normally produced in the placenta), they can test positive for pregnancy test

Amine Examples

Epinephrine, norepinephrine, histamine, serotonin, dopamine, melatonin

Steroid Structure

4 member ring structure (3 6-membered and 1 5-membered rings)

Vitamin D (Calcitriol)

Unusual story, Ex. Cod liner oil, vitamin acting like a hormone

Syntheisis of Vitamin D3 (Calcitriol) from Cholesterol

Need to remember:

25-Hydroxyvitamin D3 [25(OH)D3]

→1,25-Hihydroxyvitamin D3 [1,25(OH)D3]

(most potent version of vitamin D3)

• has hormonal effects on kidneys, intestinal tract, and bones

Chemicals of Renin-Angiotensin System

Unusual story,

• Renin (enzyme - protease)

• Angio - means artery or blood vessel

• Angiotensnogen (inactive precursor) → Angiotensin I (inactive 10 aa peptide) → Angiotensin II (active 8 aa peptide) - causes blood pressure to rise→ Angiotensin III (inactive 7 aa peptide)

Chemistry: Peptides, Polypeptides, and Proteins

• vary in size and sequence

• water soluble

• synthesized in rough ER as a “prohormone”

• Ex. Proopiomelanocorticotropic (POMC)

• Post-translationally cleaved and modified in smooth ER and Golgi

• Stored in secretory vesicles

Glycoproteins

proteins with carbohydrates attached to their surfaces

Modifications of Preprohormones

Preprohormone ————————-

Prohormone ——————

Hormone(s) —— ——

Hormone Families

• Similar genes result in similar hormones

• Oncogene hormones can bind to hormone receptors of same hormone family

• Hormone Family Ex.

  • Glycoprotein hormones (FSH, LH, TSH, hCG)

  • AVP and Oxytocin

  • Insulin, IGF-I, IGF-II, Relaxin

  • different MSH variants (Melanocyte Stimulating hormone

    • POMC can be clipped into three different MSH versions

Chemistry: Biogenic Amines

• Water soluble

• Modified amino acids: decarboxylated

• Synthesized in cytoplasm, stored in vesicles for secretion

• Ex.

  • Histamin from histidine (essential AA)

  • Serotonin from Tryptophan (essential AA)

  • Melatonin from Tryptophan (essential AA)

  • Catecholamines from tyrosine (nonessential AA)

    • Dopamine

    • Epinephrine

    • Norepinephrine

Chemistry: Steroids

• Hydrophobic

• Derived from Cholesterol (27C)

• NOT stored

• Not hormone families b/c not gene encoded

Breakdown of Cholesterol into Different Steroids

Cholesterol (27C) →

Progestines (21C, progesterone (pregnancy hormones)) →

Corticoids (21C, mineralcorticoids, glucocorticoids) OR Androgens (19C) →

Estrogen (18C)

Cannot go back up the chain

Chemistry: Iodinated Amino Acids

• Made of one amino acid each

• made only in thyroid gland

• Hydrophobic

• AA = Thyronine (derived from tyrosine)

  • Acts as a lipid, not one of the 20 regular amino acids

• Complicated synthesis: precursor is stored, but finished hormone is not (formed when needed)

  • Tetraiodothyronine (T4) = Thyroxine

  • Triiodothyronine (T3)

Chemistry: Eicosanoids

• Derived from fatty acids w/ 20 carbons

• Hydrophobic

• Not stored (synthesized when needed)

  • Prostaglandins

  • Prostacyclins

  • Thromboxanes

  • Leukotrienes

  • HETEs