Case report: A 26-year-old pregnant woman was admitted to our institution running her 30 weeks of gestation. The patient had a past history of total thyroidectomy cause of a thyroid papillary carcinoma and presented with increased supraphysiological TSH levels under 250 microg T4, while slightly hyperthyroid, from the clinical point of view. Partial resistance to thyroid replacement therapy or TSH-secreting tumour was evoked. Pituitary MRI revealed a pituitary enlargement without excluding a pituitary adenoma. To avoid further stress on pituitary a caesarean section was performed at 38 weeks of gestation. MRI 7 months later was normal, while the patient remained under high doses of T4 replacement therapy and TSH was found at the upper limits of normalcy, while T3, T4 and FTI were above normalcy.
Conclusion: We conclude that, in the absence of thyroid gland, high TSH levels due to thyroid hormone resistance could be erroneously attributed to a pituitary TSH secreting tumour, when associated with a pregnancy-related pituitary enlargement.