Osteoporosis is characterized by reduction in trabecular bone in conjunction with increased marrow cell adiposity. While these changes occur within weeks, monitoring of treatment efficacy as performed by DEXA is sensitive only to long-term changes. MRI is sensitive to bone marrow changes but is less affordable. In a recent study, we have shown that a stray-field NMR can monitor bone marrow cellular changes that are related to osteoporosis. Objectives. To demonstrate sensitivity of a low-field tabletop NMR scanner to bone marrow dynamics following hormonal treatment in rats. Methods. Two-month-old female rats (n = 36) were ovariectomized (OVX) and dosed for the ensuing 3 or 5 weeks with 20 mg/kg of PTH(1-34). Hind limbs femurs and tibiae were isolated and underwent ex vivo microradiography and histology and NMR relaxometry at 6 weeks (preventive experiment) and 11 weeks (therapeutic treatment experiment) after OVX. Results. OVX rats developed osteoporotic changes including adipogenic marrow compared to Sham and PTH treated rats. T2 and ADC NMR relaxation coefficients were found to correlate with marrow composition. Conclusions. This study suggests that stray-field NMR, an affordable method that is sensitive to the rapid cellular changes in bone marrow, may have a clinical value in monitoring hormonal treatment for osteoporosis.