Introduction: The thyroid parafollicular hormone calcitonin (CT) shows particularly high blood levels in early childhood, a period of high bone turnover, which decrease with increasing age. Data about the physiological role of CT during infancy, childhood, and adolescence are contradictory or lacking. Objective: We hypothesize that CT demonstrates age-related correlations with parameters of bone growth and turnover as well as with parameters of calcium homeostasis. Methods: 5,410 measurements of anthropometric data and venous blood samples were collected from 2,636 participants of the LIFE Child study, aged 2 months–18 years. Univariate correlations and multiple regression analysis were performed between serum CT and anthropometric indicators (height standard deviation scores [SDS] and BMI-SDS), markers of calcium (Ca) homeostasis (Ca, parathyroid hormone, 25-OH vitamin D, and phosphate [P]), bone formation (procollagen type 1 N-terminal propeptide [P1NP], osteocalcin), and bone resorption (β-CrossLaps). Results: CT was significantly associated with Ca (β = 0.26, p < 0.05) and P1NP/100 (β = 0.005, p < 0.05) in children aged 2 months–1.1 years. These relations were independent of age and sex and could not be confirmed in children aged 1.1–8 years. Independent of age, sex, puberty, P, and height SDS CT showed a significant positive relation to Ca (β = 0.26; p < 0.001) in children aged 8–18 years. Conclusions: Our findings suggest a unique association between CT and Ca in periods of rapid bone growth and point to a possible involvement of CT in promoting bone formation during the first year of life.