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22 year old male complains of testicular shrinkage; concerned for fertility
22 year old male complains of testicular shrinkage; concerned for fertility
upstream
anabolic steroid injection
body building
frequent dosage
performance
burning fat
delayed puberty
downstream
continues steroid use
difficulty/pain when urinating
enlarged male breasts
fluid retention
increased red cell count
acne
lower levels of HDL cholesterol and higher levels of LDL cholesterol
hair growth or loss
low sperm count and infertility
changes in libido
cardiovascular problems
sudden cardiac death and myocardial infarction
liver problems including tumors
tendon ruptured to degeneration of collagen
osteoporosis and bone loss
shrinking testicles
mood and anxiety disorders
reckless behavior
aggression
discontinues steroid use
withdrawals
depression
sleeping complications
decreased sex drive
background
receptors
plasma membrane receptor
water-soluble hormones bind
result: signal transduction pathway
1) hormone is signaling molecule or first messenger
2) binding of hormone to receptor forms the second messenger within the cell
3) G protein changes from inactive to active upon binding of hormone
endocrine system
endocrine glands secrete hormone which travel via bloodstream
composed of glands located throughout the body that synthesize and secrete hormones
hormone type
lipid-soluble
small, non-polar, lipophilic
diffuse across plasma membrane
upon entering cell, hormone binds to intracellular receptions in the cytosol or nucleus
form a hormone-receptor complex
hormone receptor complex bings to a particular DNA sequence within the nucleus called hormone-response elements (HREs)
result: transcription and translation of specific proteins
transport in blood: bound to plasma proteins
store in secretory vesicles: no
half-life in blood: long (most need to be metabolized by the liver)
sources: adrenal cortex, gonads, and thyroid gland
consists of: all steroid and thyroid hormones
location of receptors: usually inside cell
mechanism of action at target cell: activates genes, causing synthesis of new proteins
water-soluble
polar
unable to cross plasma membrane
need to bind to plasma membrane receptor
binding initiates signal transduction pathway
consists of: all amino acid-based hormones except thyroid hormone
sources: all other endocrine glands
stored in secretory vesicles: yes
transport in blood: usually free in plasma
location of receptors: on plasma membrane
mechanism of action at target cell: usually act through second-messenger systems
half life in blood: short (most can be removed by kidneys)
endocrine glands lact ducts
hormonal pathway from hypothalamus to the testes
hypothalamus sends a signal to the pituitary gland to release gonadotrophic substances (FSH and LH)
LH stimulates testosterone production. If too much is produced, the hypothalamus alerts the pituitary gland to make less LH
result: testes decrease testosterone levels
major endocrine glands
adrenal glands
adrenal cortex
glucocorticoids (e.g., cortisol)
stress response; increases nutrients (e.g., glucose) that are available in the blood
gonadocorticoids (e.g., dehydroepiandrosterone [DHEA])
stimulates maturation and functioning of reproduction system
mineralocorticoids (e.g., aldosterone)
regulate blood sodium and potassium levels by decreasing the sodium and increasing the potassium excreted in urine
adrenal medulla
epinephrine (EPI) and norepinephrine (NE)
"fight or flight"; prolong effects of the sympathetic division of the autonomic nervous system
pineal gland
melatonin
helps regulates body's circadian rhythm (biological clock); sexual maturation
thyroid gland
thyroid hormones: T3 (triiodothyronine) and T4 (tetraiodothyronine or thyroxine)
increases metabolism of all cells; increase heat production
parathyroid glands
parathyroid hormone (PTH)
increase blood calcium levels from calcium release bone tissue
pituitary gland (anterior)
thyroid-stimulating hormone
stimulates thyroid gland to release thyroid hormones
prolactin (PRL)
regulates mammary gland growth and breast milk production in females' may increase secretion of testosterone in males
follicle-stimulating hormone (FSH)
controls development of oocyte and ovarian follicle and sperm within testes
luteinizing hormone (LH)
induces ovulation of secondary oocyte from ovarian follicle; controls testosterone synthesis within testes
adrenocorticotropic hormone (ACTH)
stimulates adrenal cortex to release corticosteroids (e.g., cortisol)
growth hormone (GH)
release of insulin-like growth factors (IGFs) from liver; GH and IGFs function synergistically to induce growth
concepts of feedback loop
when the output of a loop influences the input
positive feedback loop
change in a given direction causes additional change in same direction
negative feedback loop
concepts of up and down regulation
down-regulation
receptors decrease in cell
up-regulation
receptors increase in cell