Endocrine Abstracts

Introduction: We present an unusual case of pituitary hyperplasia in primary hypothyroidism in a 4-year-old female in whom timely diagnosis averted invasive tests.

Case Presentation: A 4.7year old female presented with long-standing facial asymmetry. Born at term with an uneventful pregnancy, medical history and normal neonatal TSH blood spot screen. There were no symptoms of hypothyroidism. Height was 101.1 cm (-1.4SD), BMI 19.7 kg/m2 (2.5SD) and she was prepubertal. Examination revealed a smooth, modestly enlarged thyroid, right-side lip droop, while the rest of the cranial nerve and general examination were normal. Brain MRI showed an anterior pituitary lesion (13x7x14mm), displacing the optic chiasm, with a normal pituitary stalk. Blood tests showed primary hypothyroidism (Table 1), normal 09.00 ACTH and cortisol (4.7 pmol/l and 283 nmol/l respectively), elevated prolactin 798mU/l (NR <450mU/l). Thyroid peroxidase antibodies were modestly elevated (37iu/ml, NR <33.9). The patient was reviewed by the Endocrinology and Neuro-oncology Multidisciplinary Team. Pituitary changes were consistent with pituitary hyperplasia secondary to primary hypothyroidism, and facial palsy was attributed to hypothyroidism. Further tests showed negative plasma AFP and HCG, normal thyroid ultrasound scan (five weeks after the start of treatment), and bone age 5.1 years (TW2, BoneXpert). Levothyroxine replacement was initiated (12.5 mg daily for two weeks, then 25 mg). After two months, the patient was brighter and more alert, fT4 normalised, TSH fell and prolactin returned to the normal range (142mU/l, NR <500mU/l). MRI brain showed reduction of the size of the pituitary gland.

Discussion: Peripheral and entrapment neuropathies are well-documented in hypothyroidism but are rare in children. Cranial nerve dysfunction due to primary hypothyroidism has not been reported in a child previously. It is notable that this child had no symptoms of hypothyroidism, and height and bone maturity were not affected. Pituitary enlargement and hyperprolactinaemia can occur in primary hypothyroidism and typically resolve with Levothyroxine treatment. It is important to consider this diagnosis to avoid invasive tests, such as lumbar puncture for CSF tumour markers or pituitary biopsy.