JAFES-Booklet (English - pdf - 1103 Kb) - MEMS

TSH- Secreting Pituitary Macroadenoma:
A Rare Cause Of Thyrotoxicosis
Norhaliza MA, Zanariah H, Nurain MN
Endocrinology Unit, Department of Medicine, Hospital Putrajaya
TSH-secreting pituitary adenoma (TSH-oma) is a rare cause of thyrotoxicosis and accounts for
only 1-2% of all pituitary adenomas. The diagnosis is usually made much later in a patient who
has been diagnosed earlier with thyrotoxicosis. We report a case of a patient who was diagnosed
to have thyrotoxicosis during follow up of her pituitary adenoma, which was initially thought to be
a non-functioning pituitary adenoma.
A 25-year-old lady was diagnosed to have pituitary apoplexy when she presented with acute left
eye blindness and headache. MRI of the pituitary revealed the presence of a large pituitary mass
measuring 3.5 x 3.0 x 2.8 cm with suprasellar extension, compression of the optic chiasm, left
cavernous sinus and intracavernous portion of the left internal carotid artery (ICA). She underwent
transsphenoidal surgery and histological examination showed presence of infarcted
pituitary adenoma. The pituitary tissue was stained positive for prolactin and growth hormone,
while staining for ACTH, FSH, LH and TSH were negative. Serum FT4 was 13.2 pmol/l (9-19
pmol/l) and TSH was 0.38 mU/L (0.35-4.94 mU/L), while other anterior pituitary hormones were not
available.
Her vision improved post-operatively and a MRI performed three months later showed evidence
of a residual pituitary tumor measuring 2.0 x 1.8 x 1.8 cm with encasement of the cavernous
portion of the left ICA. Her thyroid function was normal; serum FT4 level was 18.1 pmol/l (9-19
pmol/l) and TSH level was 1.94 mU/L (0.35-4.94 mU/L). Other anterior pituitary hormones were
also within normal limits. However six months later, thyroid function tests noted elevated serum
FT3 and FT4 levels with non-suppressed TSH.
In view of the underlying pituitary adenoma, diagnosis of thyrotoxicosis secondary to TSH-oma
was made. This was supported by an elevated _-subunit of 3.09 IU/L (0.05-0.4 IU/L). However
TRH- stimulation test was positive, which is not classical of TSH-oma. She was planned for a trial
of medical therapy with a somatostatin analogue.
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