Congenital hypopituitarism can be caused by the absenceof hypothalamic releasing factors. Without hypothalamicstimulation, the pituitary gland does not release its hormones.Congenital defects associated with hypopituitarism range from holoprosencephaly (cyclopia, cebocephaly, orbital hypotelorism), to cleft palate (6% of cases of cleft palate are associated with GH deficiency). Septo-optic dysplasia (optic nerve hypoplasia, absent septum pellucidum, or variations of both)may result in significant visual impairment with pendular(“roving”) nystagmus (inability to focus on a target) in addition to varying degrees of hypopituitarism. The magnetic resonance imaging (MRI) findings of congenital hypopituitarismmay include an ectopic posterior pituitary gland bright spot, the appearance of a pituitary stalk transection, and/or small pituitary gland.
Diabetes mellitus (DM) is characterized by hyperglycemia andglycosuria and is an end point of a few disease processes (Table 171-1). The most common type occurring in childhood is type1 DM (DM1), which is caused by autoimmune destruction of the insulin-producing beta cells (islets) of the pancreas leadingto permanent insulin deficiency. Type 2 DM (DM2) resultsfrom insulin resistance and relative insulin deficiency, usuallyin the context of exogenous obesity. The incidence of DM1 andDM2 in the United States is increasing. Less common types ofdiabetes result from genetic defects of the insulin receptor orinherited abnormalities in sensing of ambient glucose concentration by pancreatic beta cells (see Table 171-1).
A diagnosis of DM is made based on four glucose abnormalities that may need to be confirmed by repeat testing: (1) Fasting serum glucose concentration ≥126 mg/dL, (2) a random venous plasma glucose ≥200 mg/dL with symptoms of hyperglycemia, (3) an abnormal oral glucose tolerance test (OGTT) with a 2-hour postprandial serum glucose concentration ≥200 mg/dL, and (4) a HgbA1c ≥6.5%.
A patient is considered to have impaired fasting glucoseif fasting serum glucose concentration is 100 to 125 mg/dL or impaired glucose tolerance if 2-hour plasma glucose following an OGTT is 140 to 199 mg/dL. Sporadic hyperglycemia can occur in children, usually in the setting of an intercurrent illness. When the hyperglycemic episode is clearly related to
Classic type 1 Glycosuria, ketonuria, hyperglycemia, islet cell positive; genetic component
Secondary Cystic fibrosis, hemochromatosis, drugs (L-asparaginase, tacrolimus)
Adult type (classic) Associated with obesity, insulin resistance; genetic component diabetes pregnancy only, which reverts to normal postpartum; increased risk for later onset of diabetes
Maturity-onset Autosomal dominant, onset before age diabetes of youth of 25 years; not associated with obesity or autoimmunity Mitochondrial Single-gene mutations include hepatocyte diabetes nuclear factors 1β,1α, 4α; glucokinase; insulin promoter factor 1 Associated with deafness and other neurologic defects, maternal transmission— mtDNA point mutations an illness or other physiologic stress, the probability of incipient diabetes is small (<5%).