Calcitonin participates in the control of extracellular calcium concentrations. In plasma, calcium is found in 3 fractions: protein-bound calcium, complexed calcium, and ionized calcium. The stimulation of the calcium-sensing receptor located in thyroid gland C cells by ionized calcium promotes calcitonin secretion. Calcitonin inhibits osteoclastic bone resorption, has some positive influence on renal calcium excretion, and in the long term, may impair intestinal calcium absorption.1 Although the hypocalcemic role of calcitonin is very consistent in the species in which it has been studied, the relative importance of this hormone in calcium metabolism seems to be species specific. Thus, although calcitonin is very important in the regulation of mineral metabolism in some species (eg, rats), calcitonin seems to have a minor role in others (eg, humans).2
Information about calcitonin in domestic animals is fragmentary. A specific assay for quantification of canine calcitonin has been described,3 and measurement of plasma calcitonin concentrations in horses has been recently reported,4 but no similar data are available for cats, to our knowledge.
The relationship between circulating calcitonin and ionized calcium concentrations can be studied through creation of a calcitonin-to-ionized calcium concentration curve, which describes the response of calcitonin concentration to changes in extracellular ionized calcium concentration. Calcitonin-to-ionized calcium concentration curves have been studied in clinically normal and uremic rats5–7 and in humans with chronic renal failure.8 For both species, a sigmoidal calcitonin-to-ionized calcium concentration curve has been reported. Among domestic animals, increases in circulating calcitonin concentration secondary to acute increases in ionized calcium concentration in dogs3 and horses4 have been reported. Nevertheless, no information is available regarding the dynamics of calcitonin secretion in response to changes in extracellular ionized calcium concentration in cats. The purpose of the study reported here was to characterize the dynamics of calcitonin secretion in response to experimentally induced hypercalcemia and the related changes in extracellular ionized calcium concentration in cats.
Pfizer, Madrid, Spain.
Normon SA, Madrid, Spain.
B. Braun, Melsungen, Germany.
Greiner Bio-One, Kremsmünster, Austria.
Bayer Diagnostics, Barcelona, Spain.
Scantibodies Laboratory Inc, Santee, Calif.
Immunodiagnostic Systems Ltd, Boldon, Tyne and Wear, England.
Izotop, Budapest, Hungary.
DakoCytomation, Glostrup, Denmark.
Vector Laboratories Inc, Burlingame, Calif.
SPSS, version 15.0 for Windows, SPSS Inc, Chicago, Ill.
1. Schoenmakers I, Nap RC, Mol JA, et al. Calcium metabolism: an overview of its hormonal regulation and interrelation with skeletal integrity. Vet Q 1999; 21:147–153.
3. Hazewinkel HAW, Schoenmakers I, Pelling D, et al. Biological potency and radioimmunoassay of canine calcitonin. Domest Anim Endocrinol 1999; 17:333–344.
4. Rourke KM, Kohn CW, Levine AL, et al. Rapid calcitonin response to experimental hypercalcemia in healthy horses. Domest Anim Endocrinol 2009; 36:197–201.
5. Torres A, Rodriguez M, Felsenfeld A, et al. Sigmoidal relationship between calcitonin and calcium: studies in normal, parathyroidectomized, and azotemic rats. Kidney Int 1991; 40:700–704.
6. Wang W, Lewin E, Olgaard K. Rate-dependency of calcitonin secretion in response to increased plasma Ca2+. Eur J Clin Invest 2002; 32:669–673.
7. Wang W, Lewin E, Olgaard K. Role of calcitonin in the rapid minute-to-minute regulation of plasma Ca2+ homeostasis in the rat. Eur J Clin Invest 2002; 32:674–681.
8. Felsenfeld AJ, Machado L, Rodriguez M. The relationship between serum calcitonin and calcium in the hemodialysis patient. Am J Kidney Dis 1993; 21:292–299.
9. Pineda C, Aguilera-Tejero E, Raya AI, et al. Feline parathyroid hormone: validation of hormonal assays and dynamics of secretion. Domest Anim Endocrinol 2012; 42:256–264.
10. Pineda C, Aguilera-Tejero E, Guerrero F, et al. Mineral metabolism in growing cats: changes in the values of blood parameters with age. J Feline Med Surg 2013; 15:866–871.
11. Martín-Lacave I, Rojas F, Bernabe R, et al. Comparative immunohistochemical study of normal, hyperplastic and neoplastic C cells of the rat thyroid gland. Cell Tissue Res 2002; 309:361–368.
12. Titlbach M, Velický J, Lhotová H. Prenatal development of the cat thyroid: immunohistochemical demonstration of calcitonin in the “C” cells. Anat Embryol (Berl) 1987; 177:51–54.
13. Savary KCM, Price GS, Vaden SL. Hypercalcemia in cats: a retrospective study of 71 cases (1991–1997). J Vet Intern Med 2000; 14:184–189.
14. Barber PJ, Elliott J. Feline chronic renal failure: calcium homeostasis in 80 cases diagnosed between 1992 and 1995. J Small Anim Pract 1998; 39:108–116.
15. Midkiff AM, Chew DJ, Randolph JF, et al. Idiopathic hypercalcemia in cats. J Vet Intern Med 2000; 14:619–626.
16. Mol JA, Kwant MM, Arnold ICJ, et al. Elucidation of the sequence of canine (pro)-calcitonin. A molecular biological and protein chemical approach. Regul Pept 1991; 35:189–195.
17. Toribio RE, Kohn CW, Leone GW, et al. Molecular cloning and expression of equine calcitonin, calcitonin gene-related peptide-I, and calcitonin gene-related peptide-II. Mol Cell Endocrinol 2003; 199:119–128.
18. Ramachandran R, Benfield P, Dhillo WS, et al. Need for revision of diagnostic limits for medullary thyroid carcinoma with a new immunochemiluminometric calcitonin assay. Clin Chem 2009; 55:2225–2226.
19. Naan EC, Kirpensteijn J, Kooistra HS, et al. Results of thyroidectomy in 101 cats with hyperthyroidism. Vet Surg 2006; 35:287–293.
20. Heath H III, Sizemore GW. Plasma calcitonin in normal man. Differences between men and women. J Clin Invest 1977; 60:1135–1140.
21. Guyétant S, Rousselet MC, Durigon M, et al. Sex-related C cell hyperplasia in the normal human thyroid: a quantitative autopsy study. J Clin Endocrinol Metab 1997; 82:42–47.
22. Rodriguez M, Felsenfeld AJ, Torres A, et al. Calcitonin, an important factor in the calcemic response to parathyroid hormone in the rat. Kidney Int 1991; 40:219–225.