Endocrine Abstracts

Introduction: Hypopituitarism is a rare diagnosis that is mainly due to primary pituitary neoplasms and their treatment. There are rarer causes such as hemorrhage/ischemia, traumatic brain injury, infections and infiltrative lesions.

Clinical case: We herein present an 18-year-old male patient diagnosed with acute promyelocytic leukemia at the age of 14, with no evidence of central nervous system invasion in several lumbar punctures during his follow-up. He was treated with chemotherapy (without cranial radiotherapy), being in remission for 10 months before he presented to the Endocrinology Clinic due to thyroid dysfunction: TSH 0.15 (0.27-4.20) uUI/mL and FT4 0.69 (0.80-1.67) ng/dl. He was asymptomatic, with a height of 164 cm (family target height of 167 cm) and pubertal Tanner stage 4. A second blood sample revealed a TSH of 5.32 (0.27-4.20) uUI/mL and a FT4 of 0.41 (0.80-1.67) ng/dl. Facing the suspicion of a central hypothyroidism, a pituitary panel was requested, showing low cortisol levels [1.68 (5.0-25.0) mg/dl with an inappropriately normal ACTH, a slightly high prolactin [54.4 (4.04-15.20) ng/ml], low IGF1 [60.1 (132-476) ng/ml (z-score -3.39)] and a low total testosterone leves [231 (300-1200) ng/dl] (calculated free testosterone of 3.87ng/dl). FSH and LH were normal. He was sequentially started on hydrocortisone 15 mg/day, levothyroxine 100 mg and testosterone 250 mg every 6 weeks. Brain MRI was performed and showed a discrete thickening of the pituitary stalk, measuring 4mm, with signal enhancement after gadolinium contrast, which had been known for at least 3 years. Hemochromatosis and plasmacytic hypophysitis were ruled out considering normal iron kinetics and IgG4 levels. Currently, the patient remains in leukemia remission, undergoing replacement therapy for three of the affected pituitary axes, and considering supplementation with growth hormone.

Conclusion: In this case, the laboratorial and imaging studies have not unequivocally identified the cause of hypopituitarism. Genetic combined pituitary hormone deficiency syndromes are unlikely considering his age at diagnosis, his height and normal puberty development. Pituitary leukemic infiltration remains a diagnostic hypothesis despite its rarity and considering that central nervous system involvement has never been documented in the several lumbar punctures that were performed.