Autoimmune hypothyroidism coexisting with a pituitary adenoma secreting thyroid-stimulating hormone, prolactin and alpha-subunit

J M Idiculla, G Beckett, P F Statham, J W Ironside, S L Atkin, A W Patrick

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)566-71
Number of pages6
JournalAnnals of clinical biochemistry
Volume38
Issue numberPt 5
Publication statusPublished - Sep 2001

Keywords

  • Adrenocorticotropic Hormone
  • Adult
  • Autoimmune Diseases
  • Cells, Cultured
  • Female
  • Follicle Stimulating Hormone
  • Growth Hormone
  • Humans
  • Hypothyroidism
  • Immunohistochemistry
  • Luteinizing Hormone
  • Magnetic Resonance Imaging
  • Pituitary Function Tests
  • Pituitary Gland
  • Prolactin
  • Prolactinoma
  • Protein Subunits
  • Thyrotropin

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