Sex Hormone Biochemistry Flashcards
Testosterone in the male primarily comes from ______ cells under control of _________
Leydig cells
LH
Leydig cells have an LH receptor that works via what second messenger system?
cAMP/pkA
Protein kinase A will activate what key enzyme that begins steroid synthesis?
Cholesterol esterase (produces free cholesterol)
Free cholesterol is converted to pregnenolone in the __________
mitochondria
Pregenolone is converted to testosterone in the Leydig cell within the _______
smooth ER
The majority of DHT is created where?
peripheral tissues via conversion from testosterone
The 4 critical enzymes for conversion of cholesterol eventually into testosterone are?
- p450scc (first step to pregnenolone)
- cyp17
- 3B-HSD
- C17 dehydrogenase
What is StAR protein and what’s the function?
Steriodogenic acute regulatory protein
required for ALL STEROID synthesis
brings free cholesterol across the mitochondrial membrane for conversion to pregnenolone
C17 Dehydrogenase is an enzyme involved in what reactions?
converts the mild androgen (DHEA, androstenedione) into TESTOSTERONE
5a-reductase is an enzyme involved in what reaction?
conversion of testosterone to the super-androgenic DHT
What molecules are involved in blood transport of testosterone?
60% via sex hormone binding globulin (SHBG)
38% via albumin
A deficiency in Cyp17 (17-a OHase) will result in reduction of what hormones?
no cortisol from adrenals no androgens (DHEA/androstenedione/test)
What enzyme, also known as Cyp19, is integral to estrogen synthesis?
Aromatase
Where is the aromatase enzyme located?
granulosa cells of ovary (primary)
also adipose, placenta, skin
How are estrogens transported in the blood?
60% by albumin
38% by SHBG
What function do Sertoli cells serve?
‘nurse’ cells for sperm
What are the controlling substances of the Sertoli cells?
FSH stimulates
inhibins (from Sertoli cells) block FSH
What are the 3 functions of DHT in the fetus?
develops the penis, prostate, and scrotum
