PTH (1-84) Replacement Therapy in Hypoparathyroidism: Effects on bone metabolism and structure

Publikation: KonferencebidragPosterForskning

Conventional treatment of hypoparathyroidism (hypoPT) with calcium supplements and active vitamin D analogues causes reduced bone turnover and over-mineralized bone.
We studied 62 patients with known hypoPT randomized into 2 groups of treatment with either PTH (1–84) 100 µg/d s.c. or placebo, as an add-on therapy.
We investigated the changes in bone structure and density using µCT in 44 iliac crest bone biopsies (23 on PTH treatment) obtained after 24-wks of treatment. Trabecular tunnelling was evident in 11 (48%) biopsies from the PTH-group, whereas no tunnelling was detected in the placebo group. Patients showing tunnelling had significantly higher levels of biochemical markers of bone resorption (NTX and CTX) and formation (osteocalcin, bone specific alkaline phosphatase, PINP). Compared with placebo, PTH-treatment resulted in lower trabecular thickness (Tb.Th*) (p<0.01), and trabecular bone tissue density (p<0.01), whereas connectivity density (CD) was higher (p<0.05) and structural modelling index tended to be lower indicating a change in trabecular architecture from a rod-like to a more plate like structure. The changes in Tb.Th* and CD can be explained by the intratrabecular tunnelling.
Cortical porosity tended to be higher in PTH-treated patients, especially in those with tunnelling. Occurrence of tunnelling was not associated with etiology, length of disease, concentration of PTH, ionized calcium, or 1,25-hydroxy vitamin D.

Quantitative computed tomography (QCT) at the spine and hip were performed at baseline and at week 24 in 31 patients. At the lumbar spine (L1+L2), the increase in trabecular vBMD over the study period was significantly (p=0.02) higher in the PTH group (+12.2%) than in the placebo group (-0.7%). On the contrary, total vBMD decreased more in the PTH than in the placebo group at the total hip (-1.83% vs 0.43%, p<0.05), at the trochanteric region vBMD (-3.28% vs 0.46%, p<0.03), and at the femoral neck (-3.3% vs -0.84%, p=0.12). At all three sites, there was a tendency towards an increased trabecular and a decreased cortical vBMD in the PTH treated patients.

The effect of PTH (1–84)-treatment in hypoPT is an increased bone turn-over with a decreased vBMD at cortical sites, and an increased vBMD at the trabecular sites, which is related to morphological changes in the bone microstructure with intratrabecular tunnelling and increased cortical porosity.
Udgivelsesår20 sep. 2011
Antal sider1
StatusUdgivet - 20 sep. 2011

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