Chapter 8 Steroidogenic Enzyme 17 , 20-Lyase Activity in Cortisolsecreting and Non-Functioning Adrenocortical Adenomas

The frequency of adrenal incidentalomas has been reported to range between 0.7% and 4% in abdominal computed tomography [1-5], or from 1.4% to 8.7% in autopsy series [6-8]. The widespread application of high resolution imaging techniques, such as computed tomogra‐ phy, magnetic resonance imaging and ultrasonography, has led to an increasing frequency of discovering adrenal incidentalomas. The majority of these lesions are of cortical origin, in‐ clude non-functioning adenomas, adenomas associated with pre-clinical Cushing's syn‐ drome, pheochromocytomas, adrenocortical carcinomas, myelolipomas, ganglioneuromas, metastatic tumors and cysts [9-13]. Adrenal incidentalomas are usually asymptomatic, how‐ ever many of these lesions may secrete weak precursor hormones or active hormones in in‐ sufficient amounts to cause clinically apparent disease. There are reports of several cases of adrenal incidentaloma who had no clinical evidence of Cushing’s syndrome and normal basal steroid hormone secretion, but non-suppressible serum cortisol after dexamethasone administration. These cases were regarded as “pre-clinical Cushing’s syndrome” [14-16] and many of them treated by adrenalectomy, which restored a normal cortisol suppression to dexamethasone.


Introduction
The frequency of adrenal incidentalomas has been reported to range between 0.7% and 4% in abdominal computed tomography [1][2][3][4][5], or from 1.4% to 8.7% in autopsy series [6][7][8].The widespread application of high resolution imaging techniques, such as computed tomography, magnetic resonance imaging and ultrasonography, has led to an increasing frequency of discovering adrenal incidentalomas.The majority of these lesions are of cortical origin, include non-functioning adenomas, adenomas associated with pre-clinical Cushing's syndrome, pheochromocytomas, adrenocortical carcinomas, myelolipomas, ganglioneuromas, metastatic tumors and cysts [9][10][11][12][13].Adrenal incidentalomas are usually asymptomatic, however many of these lesions may secrete weak precursor hormones or active hormones in insufficient amounts to cause clinically apparent disease.There are reports of several cases of adrenal incidentaloma who had no clinical evidence of Cushing's syndrome and normal basal steroid hormone secretion, but non-suppressible serum cortisol after dexamethasone administration.These cases were regarded as "pre-clinical Cushing's syndrome" [14][15][16] and many of them treated by adrenalectomy, which restored a normal cortisol suppression to dexamethasone.
To study the differences between non-functioning adenomas and those associated with preclinical Cushing's syndrome, we performed a comprehensive analysis of serum steroid hormone profiles in patients with such adrenocortical tumors using a combination method of high-performance liquid chromatography(HPLC) and radioimmunoassay(RIA) [17].

Subjects
We studied 22 patients with incidentally discovered adrenal masses.These lesions were seen on abdominal imaging and were diagnosed clinically and/or pathologically.From our adrenal incidentaloma cases, we selected for inclusion only patients with adrenocortical adenomas.Fifteen non-functioning adenoma cases (7 males and 8 females, mean age 59.3±13.7 yr) and seven pre-clinical Cushing's syndrome cases (2 males and 5 females, mean age 54.7±12.4yr) were studied (Table 1).As the control group, sixteen healthy adults (

Statistical analyses
We analyzed product/precursor ratios as indices of the relative activities of adrenal steroidogenic enzymes.Data are shown as mean ± SD.Variables were compared by the Mann-Whitney U test with Bonferroni correction.P values less than 0.05 were considered statistically significant.

Results
Eleven cases of non-functioning adenomas (Group I) had normal levels in DHEA and △4A compared to normal controls by simultaneous analysis (Fig. 1).In 4 cases of non-functioning adenomas (Group II), however, serum levels of DHEA and △4A were significantly decreased compared to normal controls by simultaneous analysis (Fig. 2).Other steroid hormone levels were normal in all cases of non-functioning adenomas.Therefore, we divided these patients into two groups based on the relative activities of adrenal steroidogenic enzymes by calculating product/precursor ratios.In pre-clinical Cushing's syndrome, serum levels of DHEA and △4A were significantly decreased compared to normal control values (Fig. 3) and these results were similar to values in Group II patients.17,20-Lyase activities assessed by DHEA/17-OH-Preg and △4A/17-OHP ratios were significantly decreased in Group II of non-functioning adenoma and pre-clinical Cushing's syndrome compared to Group I patients and normal controls (Fig. 4).17-Hydroxylase activities assessed by 17-OH-Preg/Preg and 17-OHP/P ratios (Fig. 5), 3β-hydroxysteroid dehydrogenase activities assessed by P/Preg, 17-OHP/17-OH-Preg and △4A/DHEA ratios (Fig. 6), 21hydroxylase activities assessed by DOC/P and S/17-OHP ratios (Fig. 7) and 11βhydroxylase activities assessed by B/DOC and F/S ratios (Fig. 8) had the same levels in all cases of non-functioning adenomas and pre-clinical Cushing's syndrome compared to normal control values.

Discussion
We examined serum steroid hormone profiles of patients with non-functioning adrenocortical adenomas and pre-clinical Cushing's syndrome.We also assessed the steroidogenic enzymatic activities of these patients by analysis of the product/precursor ratios of C21 and C19 steroid hormones in the steroidogenic pathway.Patients with pre-clinical Cushing's syndrome and a subgroup of patients with non-functioning adrenocortical adenomas had distinctly decreased adrenal androgen secretion compared with a suppressed 17,20-lyase activity.The remaining patients with non-functioning adrenocortical adenomas had completely normal adrenal androgen values and 17,20-lyase activity.
Previous reports have shown an exaggerated response of 17-hydroxyprogesterone after ACTH stimulation in some patients with incidentally detected adrenal incidentalomas [18,19].This response has been explained by existing 21-hydroxylase deficiency which may be a pathogenetic factor in the development of adrenal tumors.Macronodular adrenal hyperplasia is a frequent finding in patients with classic congenital adrenal hyperplasia, however,also about half of the heterozygous carriers in families with congenital adrenal hyperplasia were reported to have uni-or bilateral adrenal nodules on abdominal computed tomography in consecutive 4-mm scans [19].These investigators concluded that mild 21-hydroxylase deficiency is associated with the formation of adrenal incidentaloma.Other investigators have reported that the ACTH-stimulated 17-hydroxyprogesterone levels were abnormally increased in more than 50% of patients with non-hyperfunctioning adrenal adenomas [20].After unilateral adrenalectomy, this hormonal abnormality disappeared in most patients with adrenal tumors.The ACTH-stimulated 17-hydroxyprogesterone levels signifi-cantly correlated with the size of the tumors.These results indicate that tumors themselves may be responsible for the increased ACTH-stimulated 17-hydroxyprogesterone levels in patients with non-hyperfunctioning adrenal adenomas.
In this study, we demonstrated that serum DHEA and △4A levels were significantly decreased in some patients with non-functioning adrenocortical adenomas(Group II) and all those with pre-clinical Cushing's syndrome.17,20-Lyase activities were significantly decreased in Group II of non-functioning adenoma and pre-clinical Cushing's syndrome compared to Group I patients and normal controls.We found no clinical or pathological differences between Group I patients and Group II patients who had normal adrenal androgen concentrations.We have no explanation as to why there was difference between these groups.Since serum steroid hormone profiles had a similar pattern between some non-functioning adrenocortical adenomas and adenomas of patients with pre-clinical Cushing's syndrome, we suggest that the former may in time progress into pre-clinical and clinical Cushing's syndrome.There are limitations in this study such as small sample size and no tissue investigation.In the future the activity of steroidogenesis enzyme should be measured in the specimens from adrenaltissues.

Table 1 .
8 males and 8 females, mean age 51.0±7.4 yr) were used.Clinical features in cases of non-functioning adenoma and pre-clinical Cushing's syndrome Steroids