The active ingredient is essentially the same (teriparatide for Forteo and abaloparatide for Tymlos) but the formulations are not exactly the same. Osteoporosis and spinal fracture is apparently more common among mast cell disease patients than the normal population, so the inactive ingredients may be more important to consider.
Inactive ingredients in Forteo: glacial acetic acid, sodium acetate (anhydrous), mannitol, metacresol, and water for injection. In addition, hydrochloric acid solution 10% and/or sodium hydroxide solution 10% may have been added to adjust the product to pH 4.
Inactive ingredients in Tymlos (per disposable, pre-loaded injection pen containing 30 doses): 5 mg phenol, 5.08 mg sodium acetate trihydrate, 6.38 mg acetic acid, and water for injection. (From the package insert for Tymlos)
Forteo Medication Guide (from FDA)
Info from Medscape
Teriparatide in the management of osteoporosis
"fractures of the spine result in significant morbidity and are also associated with increased mortality compared with individuals without a fracture... It is the first osteoporosis treatment that leads to the formation of new bone with architecture similar to normal bone. Intense efforts have been made to understand the effect of teriparatide on antiresorptive therapy and vice versa. Although these relationships are not completely understood, the results of recent studies allow clinicians to begin to optimize therapeutic gains in bone mineral density and improve anti-fracture efficacy."