A 28-year-old married woman presents with oligomenorrhea for 1 year and infertility, now with 2 months of amenorrhea. Urine pregnancy test is negative, and ultrasound shows no abnormalities in the uterus or bilateral ovaries. Lab results show prolactin (PRL) level of 3.08 nmol/L (77 ng/ml). Before diagnosing a pituitary microadenoma, which of the following conditions must be excluded?