Term
| What are the three components of the endocrine system? |
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Definition
- Endocrine glands - secrete hormones into circulation
- Hormones - peptides, cholesterol, or tyrosine based
- Target tissue - has hormone-specific receptors and a response |
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Term
| What gland is the central endocrine gland? |
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Definition
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Term
| What is the difference between different types of hormones? |
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Definition
- Peptides - bind to GPCRs. Faster than nuclear receptors. TRH, Insulin and Glucagon, ACTH, and prolactin. Many stimulating hormones are glycoproteins.
- Steroids - bind to nuclear receptors. Cortisol, aldosterone, sex hormones
- Tyrosine - Thyroid and NE/epi |
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Term
| How are peptide hormones secreted and stored? |
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Definition
As preprohormones, the polypeptide is cleaved in the ER to a pro-hormone then packaged into vesicles by the Golgi. Inside the vesicles, cleaved into hormone.
Secretion of vesicles requires CALCIUM from L-calcium channels |
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Term
| Are cholesterol hormones stored in the body? |
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Definition
| No! They are synthesized from cholesterol --> Pregnenolone --> everything else |
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Term
| How are tyrosine hormones made? |
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Definition
In the adrenal medulla:
Tyrosine --> DOPA via tyr hydroxylase, decarboxylated to Dopamine. Dopamine hydroxylase converts to NE + methyltransferase --> epi
- Thyroid peroxidase uses thyroglobulin and iodine to make thyroxine. |
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Term
| What are the 3 types of stimuli that regulate hormone release? |
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Definition
- Humoral - changing blood levels of regulators. Ex: insulin secreted in response to elevated blood glucose. PTH released in response to high calcium. Aldosterone in response to low Na.
- Neural - stimulation of release by nerve fibers. Ex: SNS of Epi/NE and inhibition of insulin during fight or flight, PNS released GLP-1 after food
- Hormonal - release based on responses from other hormones, usually from hypothalamus. H-P axis regulates: ACTH, FSH, GH, TSH, LH, PRL |
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Term
| What are the two sections of the pituitary gland? |
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Definition
Anterior - epithelial tissue w/ a dense capillary bed, secretes many hormones
Posterior - some neural development, releases oxytocin and ADH only. Hormones actually released from hypothalamus, carried down into the posterior pituitary and out of capillaries |
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Term
| What hormones are released from the anterior pituitary? |
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Definition
- TSH - stimulates the thyroid to release thyroxine
- ACTH - adrenal cortex to release cortisol
- FSH and LH - Testes and ovaries for sex hormone regulation
- GH - affects entire body
- Prolactin - Mammary glands
- Endorphins |
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Term
| What are the different cell types in the anterior pituitary? |
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Definition
Cell types make and have receptors for hormone
- Somatotropes - Hgh, most abundant
- Corticotropes - ACTH, also abundant
- Thyrotropes - TSH
- Gonadotropes - LH and FSH
- Lactotropes - Prolactin |
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Term
| What are releasing/inhibiting hormones? |
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Definition
Secreted from the hypothalamus to the anterior pituitary
- TRH - promotes the release of TSH - thyroid
- CRH/CRF - promotes the release of ACTH
- GHRH - promotes the release of growth hormone
- GHIH - inhibits release of growth hormone. --> Stomatostatin
- GnRH - release of LH or FSH
- PIH - inhibits prolactin --> dopamine |
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Term
| What are pituitary diseases that can occur? |
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Definition
Hyperpituitarism: excess secretion as a result of a tumor
- Acromegaly - GH
- cushing's - ACTH
- SIADH - ADH
- Hyperthyroidism - TSH
Hypopituitarism: decreased due to hypothalamic or pituitary disease
- Dwarfism - GH
- Diabetes insipidus - ADH
- Hypothyroidism - TSH |
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Term
| What is the anatomy of the adrenal gland? |
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Definition
on top of the kidneys, 80% cortex and 20% medulla.
- Medulla - catecholamines (dopamine, NE/Epi)
- Cortex - Steroids such as glucocortioids, mineralocorticoids, androgens |
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Term
| What are the 3 zones of the adrenal cortex? |
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Definition
- Zona Glomerulosa - 1st layer, mineralocorticoids (aldosterone). Expresses aldosterone synthase, under control of RAAS
- Zona Fasciculata - 2nd zone, majority of the cortex. Makes glucocorticoids. 11beta-hydroxylase converts cortisol to cortisone. Affected by ACTH
- Zona Reticularis - 3rd zone, makes androgens/estrogens from DHEA. ACTH. |
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Term
| How is aldosterone made in the Zona Glomerulosa? |
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Definition
| Cholesterol --> 11-deoxycorticosterone. Has no 11-OH and also no 17-OH - no GR affinity. Converted by 11beta-hydroxylase, but will still lack GR. Corticosterone does have the 17-OH, is MR active --> aldosterone. |
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Term
| Do sex hormones have MR or GR affinity? |
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Definition
Neither! Come from DHEA, which does not have a 1-2 double bond, 11-OH, or 17-OH.
Testosterone converted by 5-alpha reductase to DHT OR by aromatase to estradiol. |
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Term
| What is the adrenal cortex controlled by? |
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Definition
The HPA axis! Hypothalamus releases CRH --> anterior pituitary releases ACTH --> adrenal gland releases cortisol
Cortisol has a negative feedback mechanism on CRH and ACTH |
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Term
| What are the net effects of glucocorticoids? |
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Definition
Net: Increase blood glucose
- form glucose (gluconeogenosis) in the liver and store it as glycogen
- Lower glucose utilization, increase lipolysis
- Fat deposition and hypoglycemia |
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Term
| What are the bad effects of glucocorticoids? |
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Definition
- electrolyte imbalances - hypokalemia
- Insulin resistance (diabetes)
- Infection and a decreased immune system
- Myopathy and weak muscles. Fat distribution
- Osteoporosis |
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Term
| What types of adrenal gland dysfunction exist? |
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Definition
Medulla - pheochromocytoma
Cortex:
- hyperadrenalism: Cushing's and hyperaldosteronism
- Hypoadrenalism: Addison's, Acute insufficiency, and hypoaldosteronism |
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Term
| What is Cushing's syndrome? |
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Definition
Increased secretion of cortisol due to an adenoma,hypothalamus, ACTH.
Similar to effects of long term steroid use |
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Term
| What causes hyperaldosteronism? |
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Definition
A tumor in the zona glomerulosa
HTN, hypokalemia (no reabsorption), increased volume, preload, and afterload --> CHF. Renin levels decreased. |
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Term
| What is Addison's disease? |
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Definition
Failure to produce adrenal hormones, usually due to atrophy. 80% autoimmune
MR - lack of aldosterone, loss of fluid volume and NA. Renin elevated.
GR - cannot maintain blood glucose homeostasis |
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Term
| How does mitotane/Lysodren work? |
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Definition
Treats hyperadrenal diseases: Cushing's
Inhibits steroid synthesis by inhibiting cholesterol-SCC enzyme and 11beta-hydroxylase.
Cholesterol cannot be converted to Aldosterone in 2 places, or to cortisol. Sex hormones still made in the gonads.
Toxicity: >4g - necrosis of the adrenal gland. |
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Term
| How does Metyrapone/Metopirone work? |
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Definition
Inhibits 11beta-hydroxylase to prevent formation of cortisol and aldosterone
11-deoxyCS has weak MR activity, works in the absence of corticosterone
Drug used for diagnosis: if cortisol levels do not go down and 11-deoxycortisol not up, problem w/ adrenal gland. CRH and ACTH increase due to negative feedback |
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Term
| What is ketoconazole used for? |
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Definition
At high doses, inhibits adrenal and gonadal steroidogenesis by inhibiting 17alpha-hydroxylase. and P450-SCC
VERY non-specific. |
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Term
| What is cyproheptadine/Periactin used for? |
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Definition
5-HT and H1 antagonist
Inhibits CRH secretion by an unknown mechanism |
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