CC - Basic Endocrinology

endocrine system

network of ductless glands that secrete hormones directly into blood

endocrine system

regulatory system of body; controlled by hormone synthesis than degradation

hormone

chemical substance that sends message to another cell in body; to regulate or control activity of other bodily functions

hormone

chemical signals produced by specialized cell, secreted into blood stream, and carried to target tissue

hormone

act at tissues or sites different from where they are synthesized and released; role in growth and development

hormone

regulated by metabolic activity by positive or negative feedback mechanism

hormone

major fxn: to maintain constancy of chemical composition of extracellular and intracellular fluids, and control metabolism, growth, fertility, and response to stress

1. T3

2. PTH

3. aldosterone

4. cortisol

hormones less secreted by elderly:

1. age

2. sex

3. time

4. younger menstruation

physiological factors affecting hormones:

andropause

slight decrease of testosterone in aging

positive feedback system

system in which increased product results to elevation of activity of system and prod rate

1. gonadal

2. thyroidal

3. adrenocortical hormones

examples of positive feedback system hormones:

thyrotrophs

cell in ant. pituitary that releases TSH & receive TRH

follicular cell

cell in thyroid gland

liver

can tell hypothalamus & ant. pituitary to decrease prod

negative feedback system

system in which increased product results to decreased activity

LH

example of negative feedback hormone:

1. long FM

2. short FM

3. ultrashort FM

types of negative feedback system:

negative feedback system

also common feedback system

long FM

feedback from hormones produced in pituitary target hypothalamus

short FM

feedback of hormones at level of pituitary gland

ultrashort FM

feedback mechanism b/w pituitary and hypothalamus

1. antagonist

2. synergistic

3. potentiation

4. permissive

5. stimulatory

6. inhibitory

hormonal interactions:

antagonist

inhibits when hormones is produced already

synergistic

amplified action of each other (2 hormones)

inhibitory

inhibits even in absence of hormone

1. endocrine

2. paracrine

3. autocrine

4. juxtacrine

5. intracrine

6. exocrine

7. neurocrine

8. neuroendocrine

types of hormone actions:

endocrine

secreted in 1 loc and released into blood circulation; binds to specific receptor to elicit physiological response

paracrine

secreted in endocrine cells and released into interstitial space

paracrine

binds to specific receptor in adjacent cell and affects its functions

autocrine

secreted in endocrine cells and sometimes released into interstitial space

autocrine

binds to specific receptor on cell of origin resulting to self-regulation of its function

juxtacrine

secreted in endocrine cells and remains in relation to plasma membrane

juxtacrine

acts on immediate adjacent cell by direct cell-to-cell contact

intracrine

secreted in endocrine cells and remained as well as function inside synthesis of origin

exocrine

secreted in endocrine cells and released into lumen of gut; affects their function

neurocrine

secreted in neurons and released into extracellular space; binds to receptor in nearby cell and affects function

neuroendocrine

secreted in neurons and released from nerve endings; interacts w/ receptors of cells at distant

1. peptides & proteins

2. steroids

3. amines

classification of hormones acc to composition/structure:

peptides & proteins

synthesized and stored w/in cell in form of secretory granules and cleaved as needed; water soluble; not bound to carrier protein

peptides & proteins

cannot cross cell membrane d/t large molecular size; produce effects on outer surface of cell

1. glycoprotein

2. polypeptide

peptides & proteins:

1. FSH

2. HCG

3. TSH

4. EPO

glycoproteins:

1. ACTH

2. ADH

3. GH

4. angiotensin

5. calcitonin

6. cholecystokinin

7. gastrin

8. glucagon

9. insulin

10. melanocyte-stimulating hormone (MSH)

11. oxytocin

12. PTH

13. prolactin

14. somatostatin

polypeptide:

steroids

lipid molecules w/ cholesterol as common precursor; produced by adrenal glands, ovaries, testes, and placenta

steroids

water insoluble; circulate bound to carrier protein; cannot travel in bloodstream, but can cross cellular membrane easily

1. aldosterone

2. cortisol

3. estradiol

4. progesterone

5. testosterone

6. activated vit D3

steroids:

amines

derived from amino acid; intermediary b/w steroid and protein hormones

1. epinephrine

2. norepinephrine

3. triiodothyronine

4. thyroxine

amines:

peptide

unbroken chain of 50 or less amino acids; hydrophilic; cannot cross cellular membranes easily

protein

amino acid length of >50

glycoprotein hormones

conjugated proteins bound to carbs

steroids

act in nucleus; binds to nuclear receptors to modify transcription and translation of genes

steroids

have delayed effect bc genes are affected

fatty acid

made up of small FA derivatives of arachidonic acid; rapidly degraded; only effective for seconds

1. circadian

2. diurnal

3. ultradian

4. infradian

biological rhythm that influence hormone measurement:

circadian rhythm

biological rhythms (endogenously generated) w/ period close to 24h

diurnal rhythm

circadian rhythm synchronized w/ day/night cycle

ultradian rhythm

biological rhythms w/ shorter period compared to circadian rhythm

infradian rhythm

biological rhythms w/ cycle that lasts longer than 24h

feeding cycle

example of ultradian rhythm

menstrual cycle

example of infradian rhythm

neuroendocrine system

maintain homeostasis and respond properly to environmental stimuli through regulated secretion of hormones, neurotransmitters, or neuromodulators

hypothalamus

portion of brain located in walls and floor of 3rd ventricle

hypothalamus

above pituitary gland; connected to posterior pituitary by infundibulum (pituitary stalk)

hypothalamus

link b/w nervous system and endocrine system

1. supraoptic nuclei

2. paraventricular nuclei

nuclei in hypothalamus that produce vasopressin and oxytocin:

hypophyseal hormones

released by neurons in anterior portion

1. thyrotropin-releasing hormone (TRH)

2. gonadotropin-releasing hormone (Gn-RH)

3. growth hormone inhibiting hormone (GH-IH)/somatostatin

4. growth hormone releasing hormone (GH-RH)

5. prolactin-inhibiting factor/hormone (PIF/PIH)

hormones released from anterior pituitary gland:

1. open-loop negative feedback mechanism

2. pulsatility

3. cyclicity

response mechanism of hypothalamus:

pulsatility

abrupt response to stimulus or pulse pattern of hormone secretion

cyclicity

nervous system regulates pattern through external signals

pineal gland

attached to midbrain; secretes melatonin

melatonin

decreases pigmentation of skin; secretions are controlled by nerve stimuli

pineal gland

receives info about state of light-dark cycle from environment and conveys info to secrete melatonin

atonia

muscle paralysis

1. accidental

2. developmental conditions

possible causes of pineal gland dysfunction:

1. NREM 1

2. NREM 2

3. NREM 3

4. REM

sleep stages/cycle for melatonin:

NREM 1

light sleep; transition for consciousness to unconsciousness; 5% of sleep; hypnic jerkq

hypnic jerk

sudden release of gamma-aminobutyric acid (GABA) and glycine responsible for muscle relaxation

NREM 2

15% of sleep; deep light sleep; transition from stage 1 to 3; muscle relaxation; 2 hours

NREM 3

deep sleep; peak GH; melatonin = sad hormone

REM

rapid eye movement; vivid or lucid dreams

atonia

prevents acting out sleep; misfiring of neurons can cause sleep paralysis which can happen w/o paranoia

REM

8-16 dreams per REM; sleep enuresis; somniloquy: murmur or conversational; somnabolism

pinealoma

tumor compressing pineal gland

pinealoma

causes def of melatonin or increased prod of melatonin

melatonin

N-acetyl-5-hydroxytryptamine

melatonin

synthesized w/in pinealocytes from tryptophan; secreted during dark period of day

melatonin

marker of phase of internal circadian clock; used in therapy for sleep disorders

melatonin

has cell protection and neuroprotection properties; may be secreted in GIT, skin, retina, BM, and placenta in autocrine or paracrine pattern

60-70 pg/mL

plasma melatonin ref value (adults)

melatonin

concentration in saliva is 3x lower than in plasma

6-sulfatoxymelatonin (aMT6s)

good marker of melatonin secretion in urine

IA

method for melatonin

1. anti-oxidant & anti-aging

2. potent free radical scavenger

3. more effective than glutathione

health benefits from melatonin:

1. posture

2. exercise

3. caffeine

false increase of melatonin d/t:

1. alcohol

2. aspirin

false decrease of melatonin d/t:

pituitary gland

hypophysis; known as master gland

pituitary gland

located in small cavity in sphenoid bone of skull called sella turcica or turkish saddle