Intro to Endocrine Flashcards
Hormones
secreted by endocrine glands and tissues
- effective at LOW [ ]
- autocrine, endocrine, and paracrine effects
- bind carrier proteins in serum
3 types of hormones
- peptide-protein
- Lipid
- Nonpeptide AA based
Bind to receptors on target cells
Free Hormone and Free Receptor form Hormone-Receptor complex
- reversible binding, saturable
- varying levels of specificity
- activates secondary messengers or transcription
Infundibulum
stalk that connects pituitary to brain
Posterior pituitary
extension of neural tissue –> controlled by hypothalamus and its hormones (ADH and oxytocin)
- hormones immediately enter circulation –> FAST response
Anterior pituitary
true endocrine gland of epithelial origin –> regulated by hormone secretion from hypothalamus (hypothalamo-pituitary endocrine axis)
- hypothalamic control is either releasing or inhibiting
- portal system
- may involve 3rd endocrine gland –> SLOW response
- hormone may act as (-) feedback regulator
Negative feedback regulation
most common mechanism
- limits amount of hormone release -> prevents snow-balling
Positive feedback regulation
Rare, reinforces snow-ball effect
Protein/peptide hormone synthesis
preprohormone synthesized and cleaved into prohormone in RER –> golgi further cleaves it into mature hormone –> packaged into secretory granules
- water soluble -> can be transported by carrier proteins but not required
Steroid hormone synthesis
derived from cholesterol -> converted to final product by enzymatic reaction (mito and smooth ER)
- produced and secreted without storage -> traverse cell membranes down [ ]
- not water soluble -> 99.9% bound to carrier proteins
Eicosanoids
biologically active lipid mediators
- signal through GPCR
- occur at low levels in tissues and are drugable targets
Hormones derived from arachdonic acid
- COX-1,2 –> prostaglandins
- 5-LO –> luekotrienes
- 12LO –> 12-HETE
- 15-LO –> 15-HETE
- Cyt P450 –> HETEs and epoxides
Amines
Catecholamines (tyrosine derived)
Thyroid Hormones -> act like steroids and bind receptors which also belong to nuclear receptor family
- production controlled by enzymes and iodine availability
Tryptophan hormones –> serotonin, melatonin
Down-regulating hormone signaling
- decreasing receptor #
2. increasing degradation of hormone cells
Up-regulating hormone signaling
- increase receptor #
2. decreasing intracellular degradation of hormone