Endocrine Abstracts

Introduction: Untreated primary hypothyroidism during adolescence can cause serious complications including impaired growth, delayed puberty, and pituitary enlargement. When imaging reveals pituitary enlargement, distinguishing between hyperplasia and adenoma is challenging. This case describes a young adult with longstanding untreated hypothyroidism who presented with delayed skeletal maturation, underdeveloped secondary sexual characteristics, and pituitary enlargement, which improved with thyroid hormone replacement.

Clinical Case: A 23-year-old man was referred to endocrinology after a distal radial fracture. Imaging incidentally showed open epiphyses, an unusual finding for his age. He had been diagnosed with primary hypothyroidism at 16 but had inconsistently taken Levothyroxine. He reported fatigue and short stature. Though he declined a detailed physical exam, lack of facial, axillary, and abdominal hair raised concerns for delayed puberty. Laboratory tests showed markedly elevated TSH and low free T4, consistent with poorly managed hypothyroidism. An insulin tolerance test confirmed growth hormone deficiency. Pituitary MRI revealed diffuse enlargement without a discrete mass. To support adherence, he began a once weekly Levothyroxine regimen, later followed by growth hormone therapy. Over several months, he reported improved mood, increased energy, and some height gain. A follow up MRI showed reduced pituitary size, consistent with reversible hyperplasia. Reassessment of his growth hormone axis is planned after stabilizing thyroid function.

Discussion: This case illustrates the consequences of prolonged untreated hypothyroidism in adolescence, including delayed epiphyseal closure, pubertal delay, and pituitary hyperplasia mimicking adenoma. It emphasizes the importance of early diagnosis, treatment adherence, and careful interpretation of pituitary imaging. Ongoing follow-up will guide the need for long-term growth hormone therapy as endocrine function normalizes.