Week 3 - Steroid Hormone Synthesis Flashcards
Xanthomas?
Yellow cholesterol rich ‘bubbles’ on skin…
What are steroid hormones derived from? Where?
Cholesterol
Synthesized in adrenal cortex and gonads
What are the different steroid hormones?
glucocorticoids cortisol -> mobilizes stored fuel
mineralocorticoids aldosterone -> regulates fluid volume
androgens testosterone -> male development
estrogens estradiol -> female development
progestins progesterone -> maintains pregnancy, female development
What are the highlited steps of steroid hormone synthesis?
Removal of most of the side chain to form pregnenolone is the first step in the synthesis of all steroid hormones; this takes place in the mitochondria. Oxidation of the #3 carbon forms progesterone.
The side chain is left on to make aldosterone and cortisol.
The side chain is completely removed to make testosterone, estradiol and estrone.
The same enzymes catalyze multiple steps
What is the important gene in steroid hormone syntheis?
Cyp21
What is congenital adrenal hyperplasia?
Congenital adrenal hyperplasia can result in mutation in steroid hormone biosynthesis genes, e.g. Cyp21.
In these patients circulating aldosterone and cortisol are decreased, and androgens are increased
What are different degress of Cyp21 mutations?
Complete mutaion will result in male characteristics in women PLUS blood pressure regulation (cortisol etc)
Partial mutation will just result in male characteristics in women..
Where do the diffeent reactions take place in steroid hormone synthesis?
In the synthesis of cortisol, the demolase and 11b-hydroxylase reactions are mitochondrial. All other reactions are cytoplasmic
What are the domains of the steroid horomone receptor?
Steroid hormones act through transcriptional regulation. They diffuse through cell membranes and bind ligand activated transcription factors
How does the transcriptional regulation by steroid hormone receptors affect cells?
Cortisol transcriptionally upregulates PEP-CK, an important gluconeogenic enzyme
HSP and GR are bound, when cortisol comes into cell (which can freely difuse through membrane) HSP is cleaved and …
Vitamine D
PTH parathyroid hormone – know the enzyme
Break in 4 ring.. Other steroid hormones don have this!
Vitamin D is an important regulator of calcium homeostasis. Its receptor is a ligand activated transcription factor, but its synthesis differs from that of steroid hormones.
Formation of the most potent form of vitamin D, 1,25-dihydroxycholecalciferol (a.k.a. calcitriol), requires reactions in the skin, liver, and kidney
PTH parathyroid hormone – know the enzyme
Break in 4 ring.. Other steroid hormones don have this!
what does vitamin do in body?
Ca regulation..
