CASE PRESENTATION: A 62-year-old man underwent biochemistry and thyroid function assessment for
asthenia. Reduced
thyroid stimulating hormone levels were associated to slightly decreased FT4 levels and low-normal FT3 levels; thyroid ultrasonography showed a multinodular
goiter. Thyroid scan with (99m)Tc-pertechnetate revealed an autonomous left nodule with suppression of the surrounding parenchyma. Pituitary investigation showed partial
hypopituitarism associated to increased
prolactin levels: 182-200 ng/ml. Magnetic resonance imaging revealed a large (2.2 cm) invasive macroadenoma. To avoid a possible high-dose hook effect, the patient's serum was diluted; the resulting PRL levels of around 1800 ng/ml prompted the final diagnosis of
macroprolactinoma. Reduced libido and
erectile dysfunction were ascertained. In addition to replacement
therapy with
L-thyroxine and
testosterone,
cabergoline was started and was progressively increased to high doses (4 g/week); this yielded a significant but incomplete reduction of PRL levels (63-99 ng/ml). Sexual function improved. The macroadenoma shrank over the first two years of
therapy, but subsequently enlarged slightly. Following stereotactic radiosurgery, the
tumor stabilized and
prolactin almost normalized (22 ng/ml) on
therapy. Over the years,
thyroid nodule volume was unmodified, but
hyperthyroidism on
L-thyroxine therapy was found, and increased FT3 levels with suppressed
thyroid stimulating hormone levels were confirmed off-
therapy. Thyroid scan confirmed the left autonomous nodule, which was successfully treated with
methimazole.
CONCLUSION: