(CSEMP037) TSH-SECRETING PITUITARY ADENOMA: 3 CASES WITH CHALLENGING DIAGNOSIS AND MANAGEMENT

Abstract:

Background: TSHoma, a rare pituitary tumor with a prevalence of one per million, causes central hyperthyroidism. 30% are co-secreting adenomas (TSH, PRL and GH). Most tumors are macroadenomas (≥ 10 mm) with risk of visual field defects, visual loss, headache, hypopituitarism. Herein we report three cases of TSHoma with challenging diagnosis.
Clinical presentation: A 47-year-old man presented with weight loss, fatigue, muscle weakness and decrease libido. Lab showed increase PRL, and an MRI sella revealed a 2.2x2.95x1.9cm adenoma. No obvious stigmata of acromegaly clinically. Additional Lab showed PRL 45, FT4 23.1, TSH 5.35, GH 2.87, IGF1 0.74ULN, then 2.04 ULN. GH trough during OGTT was 2.74. Alpha SU was 0.5ng/mL (ref < 0.5). A co-secreting pituitary macroadenoma (GH/TSH/PRL) was suspected with improving symptoms on DA and SSA. He showed early normalization of hypersecretion (TSH/GH) post transsphenoidal resection.
A 66-year-old man, known for MNG (prominent right benign nodule), HTN, CAD and A. Fib. A CT head done for left hemibody dysesthesias, showed a pituitary mass. MRI confirmed a 2.4x2.1x1.8cm adenoma with left CS and sphenoid sinus extension. Lab showed PRL 29.9, TSH 5.7, FT4 25.8, FT3 6.44, cortisol AM 450, with normal IGF1, LH, FSH, Testosterone. In retrospect, TFT in his file since 2019 were clearly in keeping with central hyperthyroidism. He complained of chronic anxiety, palpitations and weight loss. Treatment with DA resulted in normalization of TFT.
A 17-year-old woman presented with galactorrhea on OCP. PRL was > 100 and an MRI showed a 1.35cm adenoma. TSH was 5.22 , FT4 15.4. She responded well to DA, and 3 years later, after the DA had been tapered off, had severe anxiety, palpitations, weight loss, insomnia. TSH was 2.53, FT4 10.6, FT3 6.29-6.72, PRL 35.6. No adenoma on MRI. Thyroid uptake was increased 48%. Tapazole initiation and DA resumption allowed symptoms resolution.

Discussion: The diagnostic hallmark is a persistently high normal or raised free thyroxine and T3 with inappropriately normal or elevated TSH. Exclusion of interfering heterophilic antibodies and increased alpha-SU support the diagnosis. Pituitary surgery for adenoma removal, is the gold standard, but may be incomplete with high volume or local structures invasion. Euthyroidism should be achieved before surgery. SSA are the mainstay therapy for TSH suppression. DA have demonstrated successful results notably in co-secreting adenomas.

Conclusion: Clinical hyperthyroidism, monitoring and interpretation of TFTs are essential for early diagnosis of TSHomas and to prevent tumor growth with complications.