A. Maia*a (Dr), C. Cidade Rodriguesb (Dr), I. Ribeiroc (Dr), C. Amarala (Dr)

a Serviço de Endocrinologia, Diabetes e Metabolismo, Centro Hospitalar Universitário do Porto, Porto, PORTUGAL ; b Serviço de Endocrinologia, Diabetes e Metabolismo, Centro Hospitalar Tâmega e Sousa, Penafiel, PORTUGAL ; c Serviço de Neurocirurgia, Centro Hospitalar Universitário do Porto, Porto, PORTUGAL

* arianamaia@hotmail.com

Introduction: Thyrotropin-secreting pituitary adenomas are rare entities in clinical practice (0,5-3% of all pituitary adenomas), in most cases requiring appropriate investigation and exclusion of other differential diagnoses, with documentation of autonomous production of TSH.

Observations: We present a case of a 19-year-old male with a depressive syndrome and history of previous involuntary rapidly weight loss. Due to sustained mood changes, he performed an analytical study which revealed thyrotoxicosis with inappropriately elevated TSH (TSH 6.83 µU/mL [Reference range (RR) 0.27-4.2], FT3 7.79 pg/mL [RR 2.0-4.4], FT4 1.76 ng/dL [RR 0.93-1.7]). Serum glycoprotein hormone alpha-sub‐unit (α-GSU) was elevated (1,17 mUI/mL [RR 0.00-0.80] and α-GSU/TSH>1. A TRH test showed blunted TSH response. TRβ genetic test was negative. Pituitary magnetic resonance imaging revealed a microadenoma in the right side of the pituitary (8.2mmx9.7mm). The diagnosis of TSHoma was assumed and the patient started octreotide, with normalization of thyroid function after 2 months of treatment. The patient underwent transsphenoidal pituitary adenomectomy with low FT3 and FT4 in the postoperative period (FT3 1.69 pg/mL, FT4 0.50 ng/dL) and normal TSH (1.02 µU/mL). Histologically, only adenohypophysis and neurohypophysis fragments with normal characteristics were detected. In the following 3 years, the patient remained clinically euthyroid, however with analytical elevation of TSH and FT4 and FT3 over time, reaching values above the normal limit in the 3rd year post-op (TSH 4.62 µU/mL, FT3 4.42 pg/mL), raising the suspicion of thyrotrophinoma recurrence. MRI was repeated, with no imaging evidence suggestive of recurrence. Two years later, the patient presents with panic attacks and thyrotoxicosis with inappropriately elevated TSH (TSH 5.03 µU/mL, FT3 8.35 pg/mL, FT4 1.89 ng/dL). He underwent a new surgical approach, this time with histological documentation of pituitary adenoma with evidence of expression of the transcription factor PIT1, associated with positivity for TSH and PRL.

Discussion: As a rare entity, definitive diagnosis and treatment of TSHoma proved to be challenging. Surgical removal is the first-line treatment. To our knowledge, no data on recurrence rates of TSHomas in patients cured after surgery have been reported. In our patient, clinical and analytical follow-up was crucial to adequate therapeutic management.

The author has declared no conflict of interest.