Summary
During bilateral and simultaneous venous sampling of the inferior petrosal sinuses
for preoperative localization of ACTH secreting microadenomas, alpha-subunit levels,
in addition to ACTH, were determined in 9 patients with Cushing's disease.
The aim of the study was to evaluate the possible occurrence of unilateral increases
of alpha-subunit in basal conditions and the alpha-subunit responsiveness to oCRH.
All the patients examined showed a central to peripheral and an intersinus gradient
of ACTH concentrations before and/or after oCRH stimulation.
Seven patients showed a central to peripheral alpha-subunit gradient in basal conditions.
Lateralization of alpha-subunit concentrations was recorded in 4 patients in basal
conditions (intersinus gradient ≥ 1.55) and paralleled the side with the highest ACTH
concentrations. After oCRH stimulation all but one patient showed a unilateral alpha-subunit
increase in blood from the inferior petrosal sinus with the highest oCRH stimulated
ACTH increase.
The present data confirm the occurrence of an increase of alpha-subunit concentration
in response to nonspecific stimulation with exogenously administered oCRH, concurrent
with an ipsilateral increase of ACTH levels. The mechanism underlying this finding
is still unclear, although a paracrine effect from the corticotroph tumour on adjacent
pituitary tissue seems so far the most likely explanation.
Key words
ACTH - Alpha-Subunit - Cushing's Disease - Inferior Petrosal Sinuses - oCRH - Pituitary
Adenoma
