Delay in Diagnosis of Thyroid-Stimulating Hormone-Secreting Pituitary Adenomas: Clinical and Endocrinological Profiles from a Retrospective Cohort Study

Thyrotropin (thyroid-stimulating hormone)-secreting pituitary adenomas are a rare cause of hyperthyroidism that frequently presents diagnostic and therapeutic challenges. This study characterizes the clinical, biochemical, radiological, and histopathological features of thyrotropin-secreting pituitary adenomas, evaluates long-term outcomes, and identifies factors influencing remission and recurrence. We retrospectively analysed 12 patients with thyrotropin-secreting pituitary adenomas treated between January 2003 and February 2025 at a tertiary endocrine referral centre. Clinical presentation, hormonal profiles, imaging characteristics, histopathology, management, and follow-up were reviewed. Diagnostic criteria included inappropriately normal or elevated thyroid-stimulating hormone levels with increased free thyroid hormones and pituitary imaging confirming an adenoma. Remission was defined as clinical and biochemical normalization without ongoing therapy. Subgroup analysis examined the impact of diagnostic delay on tumour size, invasiveness, and outcome. The cohort comprised nine men (75%) and three women (25%) with a mean age at diagnosis of 47.8±17.2 years. Excluding one multiple endocrine neoplasia type 1 case with early detection, the mean diagnostic delay was 42.5 months (range: 4-156). Magnetic resonance imaging revealed macroadenomas in 75% of patients and Knosp grade 3-4 invasion in 41.7%. Longer diagnostic delay was correlated with significantly larger tumours (17.9±3.6 mm vs 9.8±1.0 mm; <i>p</i>=0.004). All patients underwent surgery; 50% achieved remission, while 33.3% required additional therapy (somatostatin analogues and/or radiotherapy). At a median 7.8-year follow-up, 66.7% remained in sustained remission. No patient experienced thyroid storm; transient postoperative hypothyroidism occurred in 25%. Thyrotropin-secreting pituitary adenomas often present with heterogeneous and misleading biochemical profiles leading to diagnostic delay, larger and more invasive tumours, and a greater need for multimodal therapy. Early recognition of discordant thyroid function tests-elevated free T3/T4 with non-suppressed thyroid-stimulating hormone-is critical to avoid unnecessary thyroid ablation and improve surgical outcomes.