Endocrine Abstracts

In 2003, a 60-year-old man presented to our unit non-specifically unwell. Thyroid function tests (TFTs) demonstrated an elevated fT₄ of 50 pmol/l (reference range 10–22 pmol/l)), T₃ 8.8 pmol/l (reference range 3.1–6.8 pmol/l) and TSH of 10.3 mU/l (reference range 0.5–4.5 mU/l)). Following appropriate investigations, a TSHoma was confirmed. MRI of the Pituitary confirmed the finding of a macroadenoma and the patient underwent pituitary decompression with subsequent stereotactic radio-surgery in 2004. Interval MRI Scans remained stable with no suggestion of change in residual pituitary tissue.

Last year, after having felt well for a number of years, he gave a 1-year history of feeling generally tired and lethargic, with weight gain, and a new diagnosis of depression. Thyroid function showed a rising TSH. Repeat free T₄ levels were within the reference range. Repeat MRI did not identify any change in size of the remaining pituitary tissue.

Repeat testing of his TFTs demonstrated a trending increase in TSH with a falling T₄ level (albeit still within the reference range). Thyroid peroxidase antibodies were requested which were strongly positive (2827 Iu/ml, reference range <100 Iu/ml), suggesting likely, co-existent thyroiditis.

Treatment with levothyroxine has been considered but withheld currently as the free T₄ remains in the normal range. He is under active monitoring and there has been a return to his pre-existing pattern of TFTs indicating a likely diagnosis of a transient thyroiditis.

This case highlights the importance of maintaining vigilance and an open mind for co-existent common pathologies alongside rare ones in the same organ system and that not all rising TSH values indicate relapse of TSHoma.