Describe the general pathway for anterior pituitary secretions.
Hypothalamus –> ant. pituitary –> peripheral endocrine gland –> release of third hormone
Describe the general pathway for posterior pituitary secretions.
Hormones synthesized in neuronal cell bodies in hypothalamus –> released via synapses in posterior pituitary (oxytocin and ADH)
4 structural groups of hormones:
- peptides/proteins
- amino acid derivatives
- steroids
- fatty acid derivatives (eicosanoids)
Peptide/protein hormones are _____ soluble and are often _______ to achieve an active form.
water; proteolytically cleaved
Describe the general pathway for peptide/protein hormone formation.
Gene –> mRNA –> preprohormone –> glycosylation in ER –> prohormone (in Golgi) –> secretory vessels (often in active form; other times remains a prohormone, like angiotensin)
What are the 2 groups of hormones derived from tyrosine?
Thyroid hormones and catecholamines
Describe thyroid hormones.
- “double” tyrosine with 3/4 iodines
- produced by thyroid gland
- lipid soluble
Describe catecholamines (epinephrine and norepinephrine)
- neurohormones/transmitters
- produced in adrenal medulla
- water soluble (secreted like peptide hormones)
Besides tyrosine, what are two other amino acids used for hormone synthesis? What do they make?
Tryptophan
- serotonin, melatonin
Glutamic acid
- histamine
Steroid hormones are derived from _____ and are ______ soluble.
cholesterol in the mitochondria and ER; lipid
No packaging; synthesized and immediately released. Require a globulin carrier in the blood.
List the types of steroid hormones.
- Glucocorticoids (cortisol)
- Mineralocorticoids (aldosterone)
- Androgens, estrogens, progestogens (testosterone, estradiol and estrone, progesterone)
Sugar, salt, sex
What is an example of a steroid secreted by one cell and converted to the active steroid by the target cell?
Androgen secreted by gonad and converted to estrogen in the brain.
What is the rate-limiting step of steroid hormone synthesis?
Transport of free cholesterol from cytoplasm into mitochondria; done by StAR (steroidogenic actue regulatory protein)
Cholesterol precursor comes from…
- acetate (synthesis in cell)
- cholesterol ester stores in intracellular lipid droplets
- uptake of cholesterol-containing LDLs
What is a “vitamin” derived from cholesterol?
1,25-Dihydroxy Vitamin D3
What are eicosanoids? What are they derived from?
Prostaglandins, prostacyclins, leukotrienes, thromboxanes
Arachidonic acid; these hormones active for a very short time
What are the features of the stimulus response system?
- Receipt of stimulus
- Synthesis and secretion of hormone
- Delivery of hormone to target cell
- Evoking target cell response
- Degradation of hormone
What 3 factors affect hormone concentration?
- Rate of production
- Rate of delivery
- Rate of degradation and elimination
What is neural control?
Neural input to hypothalamus stimulates releasing factors to stimulates pituitary
What is chronotropic control?
Endogenous neuronal rhythmicity
- diurnal, circadian (GH/cortisol), sleep-wake cycle, seasonal
What is a circhoral rhythm?
Release every house
What is an ultraradian rhythm?
Release > 1 hr but
What is a circadian rhythem?
Release every 24 hrs
GnRH is pulsatile. Given once hourly, ________. Given more slowly, _______. Given constantly, ________.
Normal gonadotropin secretion
Won’t maintain gonad function
Inhibits gonadotropin secretion, blocks gonadal steroid production (prostate cancer treatment)
