Prolactin-secreting Pituitary Microadenomas

—I Diagnosis and Endocrinological Evaluation—

Abstract

The authors report 12 cases of prolactin-secreting pituitary microadenomas and discuss the neuroradiological diagnosis and endocrinological evaluations.
The patients were all females between 28 and 38 years of age. Eleven cases sustained amenorrhea or oligomenorrhea with galactorrhea and one case sustained only amenorrhea. Four cases had already experienced delivery and the symptoms had continued since the last delivery in three cases. Transsphenoidal surgery confirmed the size of the tumor within 10 mm in diameter.
Plain radiograms of the sella turcica showed a normal sellar area and sellar volume but indicated two cases with a double floor of the sella and one case with localized ballooning along the anteroinferior portion of the sella. Hypocycloidal tomograms at 2 mm intervals in the lateral view showed localized `expansion' with `cortical thinning' along the sellar floor in all cases. The findings were located at the anteroinferior portion of the sella in nine cases and at the inferior or posteroinferior portion in three cases. Hypocycloidal tomograms in the AP view, however, showed abnormalities of the sellar floor in only four cases.
Conventional CT scans with contrast could not definitely delineate microadenomas. The wide width `bone window CT scan' showed localized expansion of the central portion of the sella in two cases, diffuse expansion of the sella in one case and localized lateral expansion of the sella in one case.
Subtraction magnification angiograms were normal and pneumoencephalotomograms did not demonstrate suprasellar extension of the tumors.
Results of the endocrinological examinations were compared with those of prolactin-secreting pituitary macroadenomas.
The basal serum PRL levels tended to be higher in macroadenomas but no clear separation could be made between the two groups. Retarded response of serum PRL to TRH was observed in a single case of microadenoma but not in cases of macroadenomas. Diurnal changes of serum PRL were absent both in microadenomas and macroadenomas. The L-dopa suppression effect on serum PRL was observed in nine out of 11 microadenomas and four out of five macroadenomas. The Bromocriptine suppression effect on serum PRL was observed in about half of both groups.
The L-dopa stimulation effect on serum HGH was normal in six out of ten microadenomas and one out of five macroadenomas. The insulin tolerance test on serum HGH was normal in four out of five microadenomas and subnormal in both macroadenomas. The HGH reserve was subnormal in five out of 12 microadenomas and four out of five macroadenomas.
The LH and FSH reserves for LH-RH were impaired in three and one case respectively out of 11 microadenomas and were greatly impaired (three out of six and two out of five respectively) in macroadenoma cases.
The TSH and ACTH reserves were rarely impaired both in microadenomas and macroadenomas. In conclusion, hypocycloidal tomograms in the lateral view proved very valuable in the detection of microadenomas. In the endocrinological examinations, the PRL and HGH reserves were impaired but the TSH, LH, FSH and ACTH reserves were only slightly impaired in microadenomas. In macroadenomas, however, the LH and FSH reserves were also impaired.