Animal experiment:

Rats[1]Teriparatide is administered daily to 4-week-old male rats for 1, 2, or 4 weeks with different concentrations (10, 40 μg/kg). At each time point, longitudinal growth, expressed as maximal femur length, is not statistically different between treated and control rats or between the two different treatment groups. Midfemur diaphyseal widths also do not differ between groups[1]. Rabbits[2]Forty-two female New Zealand white rabbits (17-21 weeks old) are used throughout the study. After 10 days of adaptation to their new environment, the rabbits (18-22 weeks old) are randomized into six groups of 7 animals each using the stratified weight method, as follows: 4-week vehicle administration group (4W-Veh), 4-week Teriparatide (TPTD) administration group (4W-Teriparatide: 20 μg/kg, subcutaneously [s.c.], daily), 12-week vehicle administration group (12W-Veh), 4-week Teriparatide administration + 8-week vehicle administration group (4W-Teriparatide + 8W-Veh), 4-week Teriparatide administration + 8-week lower-dose IBN administration group (4W-Teriparatide + 8W-IBN(L): 20 μg/kg of IBN, s.c., every 4 weeks), and 4-week Teriparatide administration + 8-week higher-dose IBN administration group (4W-Teriparatide + 8W-IBN(H): 100 μg/kg of IBN, s.c., every 4 weeks)[2].

Parathyroid hormone (1-34) (human), (C₁₈₁H₂₉₁N₅₅O₅₁S₂), a peptide with the sequence H2N-SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF-OH, MW= 4117.72. Parathyroid hormone (PTH), parathormone or parathyrin, is secreted by the chief cells of the parathyroid glands as a polypeptide containing 84 amino acids. It acts to increase the concentration of calcium (Ca²⁺) in the blood, whereas calcitonin (a hormone produced by the parafollicular cells (C cells) of the thyroid gland) acts to decrease calcium concentration. PTH acts to increase the concentration of calcium in the blood by acting upon the parathyroid hormone 1 receptor and the parathyroid hormone 2 receptor¹. Parathyroid hormone regulates serum calcium, It enhances the release of calcium from the large reservoir contained in the bones². It enhances active reabsorption of calcium and magnesium from distal tubules and the thick ascending limb³. It enhances the absorption of calcium in the intestine by increasing the production of activated vitamin D.

References:
1. Bieglmayer C, Prager G, Niederle B (October 2002). "Kinetic analyses of parathyroid hormone clearance as measured by three rapid immunoassays during parathyroidectomy". Clin. Chem. 48 (10): 1731–8.
2. PooleK, Reeve J (2005). "Parathyroid hormone - a bone anabolic and catabolic agent". Curr Opin Pharmacol 5 (6): 612–7.
3. Coetzee M, Kruger MC (May 2004). "Osteoprotegerin-receptor activator of nuclear factor-kappaB ligand ratio: a new approach to osteoporosis treatment?". South. Med. J. 97 (5): 506–11.