The nervous system, estrogen and osteoporosis.

Rationale:

Osteoporosis is a common disease, characterized by low bone mass and skeletal fragility resulting in an increased risk of fracture. The most prevalent cause of osteoporosis is estrogen deficiency in postmenopausal women. Estrogen replacement therapy and bisphosphonates effectively reduce fracture risk, but there are concerns about the long-term safety of these treatments. Bone mass is controlled by the balance between bone formation and resorption. The anabolic effects of estrogen on bone are presumed to be mediated by the estrogen receptor in bone. However, a recent breakthrough in experimental animals indicates an important role for the sympathetic nervous system (SNS) in bone remodelling mediated by the beta-2-adrenergic receptor. Furthermore, there are reports that the SNS is involved in the mobilization of hematopoietic stem cells.



Objective:

The objective is to study the effect of beta-agonist and beta-antagonist treatment on human bone remodeling.



Study design:

Randomized intervention trial.



Study population:

Female postmenopausal volunteers.



Intervention:

The participants will be randomized to receive hormonal replacement therapy (HRT) (estradiol/dydrogeston 1dd 1/10 mg), HRT and beta-agonist (salbutamol 1dd 4 mg), beta-antagonist (propranolol SR 1dd 80 mg) or no treatment during twelve weeks.



Main study parameters/endpoints:

The main study parameter is the difference in change of serum concentrations of bone turnover markers (procollagen type I N propeptide (P1NP) and C-terminal crosslinking telopeptides of collagen type I (CTX)) compared in the treatment and control groups(6). A secondary parameter is the change in number of circulating stem cells and osteogenic cells.

The hypothesis is that estrogen has a central effect on bone remodeling through the sympathetic nervous system.

1. Baseline;

2. 4 weeks;

3. 8 weeks;

4. 12 weeks.

The participants will be randomized to receive hormonal replacement therapy (HRT) (estradiol/dydrogeston 1dd 1/10 mg), HRT and beta-agonist (salbutamol 1dd 4 mg), beta-antagonist (propranolol SR 1dd 80 mg) or no treatment during twelve weeks.