McCumbee - Adrenal Glands And Steroids Flashcards
Endocrine glands that secrete steroid hormones
Adrenal cortex
Tests
Ovaries
Placenta
How do LDL’s enter the steroidogenic cells to be able to be used to make steroid?
Receptor-mediated endocytosis
In steroidogenic cells, cholesterol that is not immediately used is stored as lipid droplets. In order to later enter the steroidogenic pathways, these cells have _________ which is an activating enzyme that mobilizes cholesterol
Cholesterol esterase
The rate limiting step of steroid synthesis is moving cholesterol from the cytoplasm into the mitochondria. This is done by what protein?
StAR
Steroidogenic acute regulatory protein.
What do steroidogenic cells do to steroid hormones once they are synthesized
Steroid hormones are immediately released once synthesized, because steroidogenic cells have no mechanism for steroid storage.
What are the three main specific binding proteins for steroid transport?
Corticosteroid binding globulin (CBG)
Sex-steroid binding globulin (SHBG)
Vit-D-Binding Globulin
(Also will nonspecifically transport on albumin and as a free fraction)
What is the role of cholesterol acyltransferase
Cholesterol acyltransferase stores free cholesterol into lipid droplets in steroidogenic cells, keeping a reservoir of cholesterol for future steroid synthesis
Explain the steps of steroid clearance
Steroid hormones converted into inactive metabolites in the liver. Then are conjugated with sulfate or glucoronic acid, which increases their solubility. They are then excreted primarily by the kidneys.
Part of the adrenal gland
Derived from neuroectodermal cells and is essentially a modified sympathetic ganglion that secretes catecholamines
Adrenal medulla
The only zone of the cortex of the adrenal gland that expresses aldosterone synthase and is able to synthesize aldosterone
Zona glomerulosa
What enzyme converts DOC to aldosterone in the zona glomerulosa of the adrenal gland?
Aldosterone synthase
How is the transcription of StAR induced in the zone glomerulosa?
By angiotensin II triggering a Ca++ calmodulin dependent mechanism
How is transcription of StAR induced in the cells of the zona fasciculata and zona reticularis?
Via ACTH by a cAMP dependent mechanism
K+ ______ aldosterone synthesis in the zona glomerulosa
Induces
By mechanism that is initiated by the activation of voltage gated Ca channels
What is the actions of mineralcorticoids
Maintain ECF level by regulating Na+ reabsorption.
Also increase excretion of K and H
_______ is the principal adrenal androgen released by the zona reticularis
Dehydroepiandrosterone
DHEA
During pregnancy, the fetal adrenal gland produces large amounts of _________ that are converted to estrogens by the placenta
DHEA-sulfate
At what age in females and what age in males do circulating levels of adrenal androgens begin to rise?
Female 6-7
Male 7-8
Why is aldosterone the principle mineralocorticoid over cortisol and DOC in spite of their equal affinity for the mineralocorticoid receptors?
DOC- has high affinity for CBG, so less is in free fraction.
Cortisol - 11beta-HSD2 in mineralocorticoid receptor tissues converts cortisol to inactive cortisone
DHEA has a high affinity for ______ and circulates with it in the blood
Albumin
Part of the fetal adrenal that will differentiate into the different morphological zones of the adult adrenal
Outer neocortex
Part of the fetal adrenal that produces DHEAS and involutes at birth
Inner fetal zone
The major source in androgens in males after puberty
Testes
The major source of androgens in females
Adrenal
Age at which circulating levels of adrenal androgens begin to rise 6-7 in females 7-8 in males
Not apparently associated w/ the onset of puberty
Levels increase progressively thru/o adolescence
Adrenarche
-_______ is the principal glucocorticoid in humans
Cortisol
What is the half life of cortisol
90 minutes
What is the most accurate estimate of daily cortisol output?
A measurement of 24 hour urinary excretion of unmetabolized cortisol
(This despite the fact that 99% of cortisol in urine is metabolized)