‘Double Bright Spot’ in T1 Weighted Non-contrast MRI of Pituitary in Multiple Pituitary Hormone Deficiency

Abstract

An 11-d-old girl born out of consanguineous marriage presented with history of recurrent spontaneous hypoglycemia. She was delivered at term vaginally with vertex presentation. Birth weight was 2.6 kg and length was 47.4 cm (3rd percentile). There was no apparent midline defect or other dysmorphic features or any abnormal pigmentation or exaggerated physiological jaundice. There was no history of birth trauma or asphyxia.During an episode of spontaneous hypoglycemia (documented venous plasma glucose of 27 mg/dl), blood was drawn and following values were found-Growth hormone (GH) 1.3 ng/ml, Cortisol<1 mcg/dl, ACTH 3.2 pg/ml. Serum insulin was undetectable and c-peptide was 0.2 ng/ml. Her thyroid stimulating hormone (TSH) was 0.04 mcU/ml and free T4 was 0.3 ng/dl. Insulin-like growth factor binding protein 3 (IGFBP3) was 0.3 mcg/dl (normal-0.7 to 3.6 for age) and insulin-like growth factor 1 (IGF-1) was 36 mcg/dl (normal 55-327). Serum sodium and potassium were 136 meq/L and 3.9 meq/L respectively.She was diagnosed to have multiple pituitary hormone deficiency and stabilized with intravenous dextrose infusion and frequent feeds. Two mg of hydrocortisone was administered daily in divided doses. There were no hypoglycemic episodes thereafter. Levothyroxine (37.5 mcg daily) was added one day after initiating hydrocortisone. Plan for growth hormone therapy was discussed with the parents.Non-contrast MRI performed after 6 wk showed ectopic posterior pituitary. Pituitary stalk was absent. Anterior pituitary was hypoplastic and appeared hyperintense in T1 weighted image, thus creating an appearance of 'double bright spot' (Fig. 1).The combination of hypoplastic anterior pituitary and ectopic posterior pituitary can be found in congenital isolated growth hormone deficiency and multiple pituitary hormone deficiency. Ectopic posterior pituitary suggests underlying developmental defect or transection of stalk secondary to birth trauma [1]. Posterior pituitary function is usually preserved.In children and adults, rarely does anterior pituitary appear bright in noncontrast T1 weighted image. In newborns, anterior pituitary typically shows hyperintensity on T1 MRI, Fig. 1 T1 weighted non-contrast MRI of pituitary shows two bright spots-one formed by ectopic posterior pituitary (long and thin arrow), the other one represents anterior pituitary (short and stout arrow)