These causes include various inborn errors of metabolism. Problems with the gastrointestinal system such as excessive gas and acid reflux are painful conditions which may make the child unwilling to take in sufficient nutrition. Cystic fibrosis, diarrhea, liver disease, anemia or iron deficiency, Crohns disease, and coeliac disease make it more difficult for the body to absorb nutrition. Other causes include physical deformities such as cleft palate and tongue tie that impede food intake. Additionally, allergies such as milk allergies can cause endogenous FTT. FAS has also been associated with failure to thrive. Additional, medical conditions including parasite infections, urinary tract infections, other fever-inducing infections, asthma, hyperthyroidism and congenital heart disease may raise energy needs of the body and cause greater difficulty taking in sufficient calories to meet the higher caloric demands, leading to FTT. Exogenous (or "nonorganic")
Exogenous causes are due to caregiver actions, whether unintentional or intentional. Examples include physical inability to produce enough breastmilk, inappropriate feeding schedules or feeding technique, and mistakes made in formula preparation. In developing countries, conflict settings, and protracted emergencies, exogenous FTT may more commonly be caused by chronic food insecurity, lack of nutritional awareness, and other factors beyond the caregivers control. As many as 90% of failure to thrive cases are non-organic. Mixed
Both endogenous and exogenous factors may co-exist. For instance, a child who is not getting sufficient nutrition for endogenous reasons may act content so that caregivers do not offer feedings of sufficient frequency or volume.
Additionally, medical providers will inquire about any medical conditions that other members of the family may have, as well as assess the psychological and social circumstances of the child and family.Next, a complete physical examination may be done, with special attention being paid to identifying possible organic sources of FTT. This could include looking for dysmorphic features (differences in physical features that may indicate an underlying medical disorder), abnormal breathing sounds, and signs of specific vitamin and mineral deficiencies. The physical exam may also reveal signs of possible child neglect or abuse.Based on the information gained from the history and physical examination, a workup can then be conducted, in which possible sources of FTT can be further probed through blood work, x-rays, or other tests. Laboratory workup should be done in response to specific history and physical examination findings. Medical providers should take care not to order unnecessary tests, especially given estimates that the usefulness of laboratory investigations for children with failure to thrive is 1.4%. Initial bloodwork may include a complete blood count (CBC) with differential to see if there are abnormalities in the number of blood cells, a complete metabolic panel to look for electrolyte derangements, a thyroid function test to assess thyroid hormone activity, and a urinalysis to test for infections or diseases related to the kidneys or urinary tract. If indicated, anti-TTG IgA antibodies can be used to assess for celiac disease, and a sweat chloride test can be used to screen for cystic fibrosis.