PARTIAL ECTOPIC POSTERIOR PITUITARY GLAND IN A CHILD

A VARIANT OF AN ECTOPIC NEUROPHYPOPHYSIS SYNDROME

Abstract

INTRODUCTION
Developmental abnormalitiy of the posterior pituitary can lead to an ectopic posterior pituitary at the median eminence or along the pituitary stalk with partial or complete pituitary stalk agenesis. An ectopic posterior pituitary gland is associated with isolated growth hormone or multiple anterior pituitary deficiencies but with normal posterior pituitary function. A partial ectopic pituitary gland is a less common entity described whereby there is presence of both an orthotopic (normally located) and ectopic neurohypophysis.

RESULTS
The patient first presented at 2 months old with prolonged jaundice. Thyroid function screening showed central hypothyroidism and she was started on L-thyroxine. She presented again at 2 years 10 months old with a hypoglycaemic seizure. Subsequently she was referred for further paediatric endocrine evaluation. Her IGF-1 was < 20mcg/L and glucagon stimulation test confirmed severe GH deficiency (peak GH 0.54ug/L) with an optimal cortisol peak of 698 nmol/L. Pituitary/brain MRI shows a hypoplastic pituitary gland and absence of pituitary stalk. There was a bright spot at the normal expected site of the neurohypophysis in the posterior sella with an additional ectopic focus of high signal intensity on T1-weighted imaging at the infundibulum measuring 3mm x 3mm which was most likely an additional and ectopic focus of the posterior pituitary gland. The pituitary stalk was not visualized. She was started on recombinant GH therapy and remains on L-thyroxine. Regular monitoring of her 8 am cortisol remains normal and she did not have symptoms or biochemistry suggestive of diabetes insipidus on follow-up.

CONCLUSION
Partial ectopic posterior pituitary gland is a variant of ectopic posterior pituitary that is a rarely described imaging entity. Although there is a wide differential diagnosis for T1-hyperintensities (e.g., lipid-containing lesions, protein, metallic substances, methemoglobin and calcifications) on MRI, the diagnosis can be narrowed with the aid of additional MRI sequences and clinical manifestations.