Fact-sheet: Pituitary stalk interruption syndrome
Updated on 09/17/2021 at 12:16 PM
View all RADEOS cases associated with this fact-sheet
Definition
Pituitary stalk interruption syndrome (PSIS) is a congenital pituitary anomaly resulting in hypopituitarism and generally characterized by a triad:
- a very thin or interrupted pituitary stalk
- an ectopic posterior pituitary (EPP) or its absence
- hypoplasia or aplasia of the anterior pituitary, visible on MRI.
In some patients, the anomaly may be limited to an EPP (also called ectopic neurohypophysis) or an interrupted pituitary stalk.
The prevalence of PSIS is unknown, but approximately 1,000 cases with or without the complete triad have been reported to date.
Clinical features
In the neonatal period, PSIS presents with Low bloog glucose Hypoglycemia, prolonged jaundice, congenital anomalies with micropenis and/or Malpositioned testis, suggestive of hypothalamic-pituitary deficiency.
PSIS is also associated with a higher than normal frequency of breech presentation, cesarean delivery, and/or low Apgar score. The birth conditions are probably more a consequence than a cause of PSIS.
Later in childhood, suggestive signs include short stature, low growth rate, and/or a difference of more than 1.5 SD between target height and actual height.
Epilepsy, hypotension, and/or intellectual disability may be present.
PSIS may be associated with Septo-optic dysplasia and Fanconi anemia. The exact etiology of PSIS is unknown.
Laboratory findings
Mutations in the transcription factor HESX1 (3p21.2-p21.1) have been found in patients with isolated PSIS and/or PSIS associated with Septo-optic dysplasia. Mutations in the LHX4 gene (1q25) have also been associated with PSIS. In most cases, a genetic cause is not identified, but the existence of familial forms and the association of PSIS with micropenis and congenital anomalies, particularly ocular ones, suggest a prenatal origin.
The diagnosis, suspected based on the clinical presentation, relies on a low peak growth hormone (GH) level on stimulation testing along with a low insulin-like growth factor 1 (IGF-1) level.
The diagnosis of PSIS implies a permanent GH deficiency. It must then be determined whether the GH deficiency is isolated or associated with other anterior pituitary deficiencies (which is the case in 70% of PSIS).
MRI
MRI confirms the diagnosis by showing the EPP as a hyperintense nodule in the region of the infundibular recess of the third ventricle.
Differential diagnosis
If SITH is confirmed by MRI, there is no differential diagnosis.