Endocrine Abstracts

JOINT2815

Association between pituitary adenomas (PA) and differentiated thyroid cancer (DTC) requires an individualized approach. On one hand, pituitary neurosurgery and radiotherapy, as well as some drugs might impact the TSH secretion due to post-procedural hypopituitarism. On the other hand, classic treatment of DTC includes total thyroidectomy (TT), radioactive iodine therapy, and follow-up monitoring using stimulated thyroglobulin (sTgl). Herewith we describe four cases of patients with DTC and associated thyrotropic insufficiency due to simultaneous PA, underlying the importance of recombinant human TSH (rhTSH) stimulation for optimal management. • A 45-year old acromegalic male is presenting with papillary thyroid carcinoma (PTC), who underwent a TT, and an associated thyrotropic insufficiency on account of a GH-secreting pituitary adenoma treated with transsphenoidal surgery (TSS) and additional SMSa. In the need of a RAIU for the PTC follow-up, his replacement therapy was withdraw 4 weeks, but the TSH remained low (12.85 mUI/L), under the optimal value required (>30mU/L). After rhTSH raised TSH to 72.66 mUI/l, allowed RAIU and stimulated Tgl< 0.2 ng/ml, certifying the cure of DTC. • A 56-year old female presented with PTC and a history of macroprolactinoma irradiated twice (1985) and then treated with dopaminergic agonists, which resulted in panhypopituitarism. After performing TT for PTC, followed by one month LT4 withdraw in order to do radioiodine ablation, her TSH was only 3.94 mUI/L. After rhTSH injection, her TSH increased to 85.36 mUI/lallowing I¹³¹ treatment and sTgl=3.47 ng/ml. • A 63-year old male with history of macroprolactinoma with pituitary apoplexy, treated with TSS and subsequent gonadotrophic and thyrotropic insufficiency, underwent TT for PTC. Four weeks off-treatment, TSH=13.44 mUI/L. After rhTSH, TSH=49.1 mU/l, RAIU excluded any remnant thyroid tissue and Tgl = 0.2 ng/ml, certifying the cure of DTC. • A 65-year old female with a non-functioning pituitary adenoma and simultaneous PTC, underwent firstly TT (03.2023) and 4 months later the TSS for PA resulting in a thyrotropic deficiency. This time she underwent I¹³¹ therapy (10.2023) with an off-treatment (TSH=1.72 mU/l, fT4=0.3 ng/ml), without rhTSH, with a very low efficiency resulting in the need of a second radioactive iodine treatment.

Conclusion: TSH deficiency in hypopituitarism associated with DTC makes the radioactive iodine treatment or the RAIU/Tgl for the management of thyroid cancer less effective, unless rhTSH is used.