A 20-d-old boy was referred to our department because of hyperthyrotropinemia at neonatal mass screening and diagnosed with neonatal transient hyperthyrotropinemia. A follow-up examination when the patient was 5 mo old revealed severe
hypercholesterolemia.
Familial hypercholesterolemia was first suspected because of the patient's significantly high levels of total and
low-density lipoprotein cholesterol. The parent's serum
lipid profiles were examined and found to be normal. He was completely breast-fed until 6 mo of age. Breast milk was still the main source of food for a period following weaning. At 14 mo old, the patient was weaned completely from breast milk, and his serum
cholesterol levels decreased dramatically. According to the normal
lipid profiles of the patient's parents and the spontaneous normalization of serum
cholesterol levels after complete weaning from breast milk, breast-feeding was suggested to be responsible for his transient severe
hypercholesterolemia. It is well documented that breast-fed infants have higher serum
cholesterol levels than formula-fed infants. However, there is no reported case with severe
hypercholesterolemia equivalent to or higher than the levels observed in the case of
familial hypercholesterolemia. Although the exact mechanism is unknown, it is necessary to consider that a small number of cases develop severe
hypercholesterolemia related to breast-feeding.