A 59-year-old, healthy, non-smoking and asymptomatic woman was referred from Primary Care to the endocrinology clinic in August 2003 for subclinical hypothyroidism.
She had no goiter and two recent determinations of thyroid function had shown normal serum free thyroxine (FT4) levels and elevated thyrotropin (TSH) levels: 13.55 and 13.86 mcUI/2).
Anti-thyroid peroxidase antibodies (Ac anti-TPO) were positive at high titres.
With the diagnosis of autoimmune subclinical hypothyroidism without goiter, treatment was initiated with 50 mcg/day of oral thyroxine (1 mcg/kg weight), and it was found in analysis performed at 6 and 12 months that this dose was normal.
In December 2004, the patient came spontaneously to the consultation to comment that in the last month she had noticed protrusion of the eyeballs, conjunctival irritation and tears.
The examination carried out by the Ophthalmology Service showed a moderate bilateral exophthalmos and a normal ocular motor.
The diagnosis of probable thyroid disease (not considered as indicated complementary tests) was established. The patient was advised to take artificial contraceptives, and the Endocrinology Section to investigate a possible GD.
Serum levels of FT4 and TSH (normal with treatment), anti-TPOAb (positive) and anti-TSHr receptor antibodies (Ac anti-TSHr) were then determined, which were also positive: 40.
Since these antibodies are virtually pathognomonic of GD, and since normal thyroid function in this disease is less rare than hypofunction, treatment with thyroxine may not be established to check the intrinsic thyroid status.
After two months without oral thyroxine, FT4 was 0.47 ng/dL (VN: 0.7-1.7) and TSH was 54.01, so the patient was diagnosed with primary hypothyroidism and restarting in the sinus.
To date (April 2006), exophthalmos has remained unchanged (annual reviews in Ophthalmology), and thyroid function -with treatment- is normal.
