93symmetrymog
Iron
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Parathyroid hormone intermittently administered increases bone mass in rats though it could in theory be applied to humans through mechanisms involving local growth factors in bone tissue. Nearly all bone density evidence from PTH is from endochondral ossification sites like vertebrae yet the study used daily subcutaneous hPTH 1-34 injections in male rats at doses of 4, 10 or 40 micrograms per kg for 2, 4, 8 or 12 weeks showing time- and dose dependent rises in lumbar spine bone mineral density up to 39 percent. This anabolic effect coincided with progressive increases in bone matrix-associated IGF-I apparent after four weeks and persisting through week 12 and TGF-beta1 after eight weeks also sustained to week 12 with no changes in circulating IGF-I or IGF-II indicating direct local PTH action on bone. While PTH primarily drives appositional bone formation rather than extensive modeling in craniofacial sites like zygoma and mandible it does thicken cortical bone via periosteal activity which could in theory enhance mandibular and zygomatic mass but there's weak evidence on that. These data support IGF-I and TGF-beta1 as local mediators of PTHs anabolic effects on bone metabolism consistent with in vitro evidence where PTH stimulates their production in osteoblasts. Clinical evidence from human trials shows PTH fragments like PTH 1-34 restore spinal bone in osteoporotic patients and prevent estrogen-deficiency bone loss aligning with this growth factor mechanism in postmenopausal women and men on daily injections. The time-dependent matrix rises match observed bone gains positioning IGF-I and TGF-beta1 as key to PTHs efficacy in human osteoporosis therapy for sustained formation over months.
"The human studies show BMD gains but no increase in actual vertebral height So even though that rat study shows increases BMD you can’t extrapolate it to much"
"In height it doesn’t mean much, as we established, and in terms of craniofacial growth, all you’re going to get is a slight increase in density"
"It doesn’t increase bone modeling though which gives you that projection. And the evidence is weak for craniofacial density in humans still"
" The only real studies for craniofacial growth are done on the mandibular condyle with PTH analogs and that’s obviously different than something like the zygomas"
credits to brandon for his thoughts on this topic
pmc.ncbi.nlm.nih.gov
"The human studies show BMD gains but no increase in actual vertebral height So even though that rat study shows increases BMD you can’t extrapolate it to much"
"In height it doesn’t mean much, as we established, and in terms of craniofacial growth, all you’re going to get is a slight increase in density"
"It doesn’t increase bone modeling though which gives you that projection. And the evidence is weak for craniofacial density in humans still"
" The only real studies for craniofacial growth are done on the mandibular condyle with PTH analogs and that’s obviously different than something like the zygomas"
credits to brandon for his thoughts on this topic
Parathyroid hormone increases the concentration of insulin-like growth factor-I and transforming growth factor beta 1 in rat bone - PMC
Intermittent treatment with parathyroid hormone (PTH) increases bone mass in experimental animals and humans. In vitro studies have suggested that the anabolic effect of PTH may be mediated by local growth factors. However, the relevance of these ...
pmc.ncbi.nlm.nih.gov
