Although most patients with only optic nerve involvement lead normally productive lives, those with accompanying endocrine dysfunction or other midline cerebral abnormalities are more at risk for on-going intellectual and other disabilities. Epidemiology
Optic nerve hypoplasia (ONH) is a congenital condition in which the optic nerve is underdeveloped (small). Many times, de Morsier’s Syndrome or septo-optic dysplasia (SOD) is associated with ONH, however, it is possible to have ONH without any additional issues like SOD. SOD is a condition that can involve multiple  problems in the midline structures of the brain, stemming from miswiring of the brain and central nervous system. Besides having small optic nerves, persons with ONH can have agenesis of the corpus callosum, absence of the septum pellucidum, maldevelopment of the anterior and posterior pituitary gland, and anomalies of the hypothalamus. Because of this, all children with ONH are at risk for developmental delays and hormonal deficiencies, regardless of severity of ONH, or whether abnormalities are visible by MRI. ONH is the single leading cause of permanent legal blindness in children in the western world. The incidence of ONH is increasing, although it is difficult to estimate the true prevalence. Between 1980 and 1999, the occurrences of ONH in Sweden increased four-fold to 7.2 per 100,000, while all other causes of childhood blindness had declined. In 1997, ONH overtook retinopathy of prematurity as the single leading cause of infant blindness in Sweden, with 6.3 in every 100,000 births diagnosed with ONH.
A poorly functioning pituitary gland may also cause a lack of thyroid hormone, leading to central hypothyroidism. Thyroid hormone is critical for growth and brain development, especially during the first few weeks to months of life. Children with untreated hypothyroidism are at high risk of mental retardation; thus, early detection is crucial. Central hypothyroidism can be diagnosed by a low or normal thyroid-stimulating hormone (TSH) in the presence of a low level of free T4. Free T-4 should be checked annually for at least four years.Cortisol is made in times of stress. Approximately one-quarter of patients with ONH have adrenal insufficiency, meaning they do not produce enough cortisol on a daily basis or in stressful situations.Imbalances in sex hormone may result in a delay in sexual development (puberty) or precocious puberty. Sex hormones may be tested from birth to 6 months of age (during a mini-puberty). Hyperprolactinemia (an excess of prolactin) often occurs in conjunction with ONH and indicates either dysfunction of the hypothalamus or a disconnect between the hypothalamus and pituitary gland. Hyperprolactinemia often correlates with development of obesity in children with ONH.The posterior pituitary gland produces anti-diuretic hormone (ADH), which controls outflow of water from the body by urine. ADH deficiency, also known as diabetes insipidus (DI), results in dehydration and high sodium levels in the body from excessive urination. Testing for DI involves blood and urine testing, including water deprivation tests, to determine ADH creation levels by the body.