Autoimmune hypothyroidism coexisting with a pituitary adenoma secreting thyroid-stimulating hormone, prolactin and alpha-subunit.
A 44-year-old woman presented to her GP with excessive tiredness. She had positive thyroid microsomal and thyroglobulin autoantibodies and was found to have an elevated serum thyroid-stimulating hormone (TSH) concentration of 8.37 (normal = 0.15-3.5)mU/L and a low normal total thyroxine (T4) of 86 (reference range 60-145)nmol/L. She was rendered symptom free on a dose of 150 microg of thyroxine per day. However, her TSH failed to return to normal, and following a further increase in her thyroxine dose she was referred to the endocrine clinic for further assessment. Her TSH at this stage was 14mU/L, free T4 (fT4) 28 (normal = 10-27)pmol/L and free T3 (fF3) 10 (normal = 4.3-7.6)pmol/L. She denied any problems with adherence to her medication. Her serum prolactin was elevated at 861 (normal = 60-390)mU/L. A pituitary tumour was suspected and an MRI scan showed a macroadenoma of the right lobe of the pituitary, extending into the suprasellar cistern. The tumour was resected trans-sphenoidally. Electron microscopy showed a dual population of neoplastic cells compatible with a thyrotroph cell and prolactin-secreting adenoma. Immunocytochemistry and cell culture studies confirmed the secretion of TSH, prolactin and alpha-subunit. Postoperative combined anterior pituitary function tests did not demonstrate any deficiency of anterior pituitary hormones. A repeat MRI scan showed no significant residual tumour; however, her serum TSH and prolactin levels remained high and she was given a course of pituitary irradiation. This case illustrates the difficulty of diagnosing a TSHoma when it coexists with autoimmune hypothyroidism. We believe the combination of pathologies reported here is unique.
Idiculla
J M
JM
Endocrine Department, Royal Infirmary, Edinburgh, UK.
Beckett
G
G
Statham
P F
PF
Ironside
J W
JW
Atkin
S L
SL
Patrick
A W
AW
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000328:Adult; D001327:Autoimmune Diseases / Q000150:complications* / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D002478:Cells, Cultured; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D010901:Pituitary Function Tests; D010902:Pituitary Gland / Q000473:pathology / Q000503:physiopathology; D011388:Prolactin / Q000378:metabolism; D015175:Prolactinoma / Q000150:complications* / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D021122:Protein Subunits; D013972:Thyrotropin / Q000378:metabolism*
D021122:Protein Subunits; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013006:Growth Hormone