A Multicenter, Multinational Clinical Assessment Study for Pediatric Patients With Achondroplasia

Inclusion Criteria: * Parent(s) or guardian(s) willing and able to provide signed informed consent after the nature of the study has been explained and prior to performance of any research-related procedure. Also, willing and able to provide written assent (as needed) after the nature of the study has been explained and prior to performance of any research-related procedure. * Aged 0 to \<= 17 years, inclusive, at study entry. * Have ACH, documented by clinical diagnosis * Are ambulatory and able to stand without assistance (not applicable for infants) * Are willing and able to perform all study procedures as physically possible. Exclusion Criteria: * Have hypochondroplasia or short stature condition other than ACH (e.g., trisomy 21, pseudoachondroplasia) * Have any of the following disorders: * Hypothyroidism * Insulin-requiring diabetes mellitus * Autoimmune inflammatory disease * Inflammatory bowel disease * Autonomic neuropathy * Have an unstable clinical condition likely to lead to intervention during the course of the study, including progressive cervical medullary compression * Growth plates have fused * Have a history of any of the following: * Renal insufficiency * Anemia * Cardiac or vascular disease, including the following: * Cardiac dysfunction (abnormal echocardiogram \[ECHO\] including left ventricle \[LV\] mass) at Screening Visit * Hypertrophic cardiomyopathy * Congenital heart disease * Cerebrovascular disease, aortic insufficiency * Clinically significant atrial or ventricular arrhythmias * Current treatment with antihypertensive medications angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, diuretics, beta-blockers, calcium-channel blockers, cardiac glycosides, systemic anticholinergic agents, any medication that may impair or enhance compensatory tachycardia, drugs known to alter renal function that is expected to continue for the duration of the study * Have been treated with growth hormone, insulin-like growth factor 1 (IGF-1), or anabolic steroids in the previous 6 months or long-term treatment (\> 3 months) at any time * Have had regular long-term treatment (\> 1 month) with oral corticosteroids (low-dose ongoing inhaled steroid for asthma is acceptable) * Concomitant medication that prolongs the QT/QTc interval within 14 days or 5 half-lives, whichever is longer, before the Screening visit * Have used any other investigational product or investigational medical device for the treatment of ACH or short stature * Have had bone-related surgery or expected to have bone-related surgery during the study period. Subjects with previous limb-lengthening surgery may enroll if surgery occurred at least 18 months prior to the study and healing is complete without sequelae. * Have any condition that, in the view of the Investigator, places the patient at high risk of poor compliance with the visit schedule or of not completing the study. * Concurrent disease or condition that, in the view of the Investigator, would interfere with study participation