Quiz 2 Flashcards
steroid hormones are synthesized from
cholesterol
Steroid hormones act through — and — mechanisms
genomic (classical) and nongenomic
The classical mechanism is through interactions of the
steriod hormones with cytoplasmic or nuclear receptors
Hormone-recptor complexes bind to
specific seuences in the DNA (hormone response elements, HRE)
Hormone-recptor complexes interact with
interact with co-activators/corepressors to effect gene expression.
Membrane HRs (hormone receptors) also exert modulatory effects on nuclear HR through signaling pathways targeting
nuclear HR and co-activators (e.g., phosphorylation changes)
Membrane receptor binding of steroid hormones initiates various signaling pathways and activates other transcription factors that can lead to transcription of some genes without
HREs
Sex hormones or their analogs are used in the treatment of a variety of
diseases
Analogs of sex hormones also have a number of ”—” uses that can have serious side effects
recreational
Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol) are prohormones that require
metabolic activation to generate the most active chemical form
Vitamin D3 is required for
proper calcium and phosphorus absorption needed to build strong bones and teeth
what is the best source of vitamin D3?
the sun
The sun is the best source of Vitamin D because it converts
7-dehydrocholesterol to Vitamin D3
many — are also high in vitamin D3
foods
Diary products in the U.S. are supplemented with Vitamin D3 to help avoid
deficiency state
The activation pathway involves a UV-activated step which means that Vitamin D3 must either
be obtained via the diet or by produced via a sunlight activated step and then transported to the liver for conversion to 25-(OH)D3
25-(OH)D3 is measured to assess
adequate intake of Vitamin D
It is converted in the kidney (and a few other tissues such as skin and immune system cells) to the active form of
1,25-(OH)2D3
Vitamin D metabolites are transported in the blood bound to
Vitamin D binding protein
1,25-(OH)2D3 functions to regulate
Ca2+ and phosphate homeostasis
It binds to the Vitamin D Receptor, which is a transcription factor that forms a heterodimer with the RXR to
regulate transcription. It can also act via membrane receptors
1,25(OH)2D3 is synthesized in the kidney in response to
PTH
PTH is secreted when
serum Ca2+levels are low
Rickets and osteomalacia are diseases caused by
Vitamin D deficiency