Steroid Contents and Cortical Steroidogenic Enzymes in Non-Hyperfunctioning Adrenal Adenoma
HIROMICHI SUZUKI, HIROTAKA SHIBATA, TAKASHI TAKITA,
SHU WAKINO, TADASHI OGISHIMA*, YUZURU ISHIMURA* AND TAKAO SARUTA
Departments of Internal Medicine, and *Biochemistry, School of Medicine, Keio University, Tokyo 160, Japan
Abstract. The recent increasing use of ultrasound and computed tomography has revealed numbers of incidentally discovered adrenal tumors. Many studies have focused on their surgical management, but the biological characteristics of these adrenal tumors have remained unclear. Adrenal tumors were resected from 10 patients who underwent gastrectomy or cholecystectomy. No signs or symptoms of adrenal hormone excess or deficiency were evident either before or after the operation. Moreover, after surgery, no major differences in signs and symptoms including blood pressure levels were observed. Before surgery, neurogenic tumors and cysts were excluded by enhanced magnetic resonance imaging. Steroid contents and both the activities and amounts of steroidogenic cytochrome P-450s in the adreno- cortical adenomas of these patients were examined. Microscopic examination revealed that the tumors were surrounded by a thin, non-intact capsule; the surrounding cortex was not atrophic and apparently normal; and the cells of both the tumor and adjacent portions were arranged in nests and cords. Mea- surements of all steroid content (pregnenolone, progesterone, corticosterone, 11-deoxycorticosterone, 18- hydroxydeoxycorticosterone, cortisol, and dehydroepiandrosterone) except aldosterone in 5 resected ad- renal tumors were within the normal ranges for the adrenals of 5 patients with renal cell carcinoma. Aldosterone content in tumor portions was significantly lower than in the apparently normal adrenals. Although in both tumor and adjacent portions of another 5 resected adrenal tumors the activities and amounts of cytochrome P-450s (P-450scc, P-450118 P-450aldo, P-45017% and P-450(21) were also within the normal ranges, the activities of P-450scc and P-45017g in the tumor portion were greater than those in the adjacent portion. Grossly well-demarcated yellowish-brown tumors of the adrenal gland were observed in all the cases of adrenal tumor. The above results suggested that adrenal incidentalomas produce adrenal steroids through steroidogenic enzymes in both the tumor and adjacent portions. In addition, decreases in aldosterone content and increases in the activities of P-45017g in tumor portions suggest the shift of steroidogenesis from a mineralocorticoid pathway to a glucocorticoid pathway.
Key words: Adrenal tumor, Adrenal incidentaloma, Steroid enzymes, Cytochrome P-450. (Endocrine Journal 41: 267-274, 1994)
ADRENAL INCIDENTALOMAS have been dis- cussed mainly in terms of whether they should be resected or left in place [1-3]. These studies indi- cated that the tumors should be removed if 1) they are hormonally active, 2) they are potentially ma-
lignant, 3) they are of neurogenic origin such as pheochromocytomas and 4) the size of the masses on computed tomographic (CT) scans is more than 5 cm.
Compared to such surgical approaches, there have been relatively few examinations of the bio- logical characteristics of adrenal incidentalomas, such as steroid content and enzymes involved in the steroidogenesis of benign adrenal cortical adenoma which were the most frequently found
adrenal incidentalomas. One of the main reasons for this is the diverse causes of adrenal incidentalomas including metastasis, cyst, myelolipoma, adrenal cortical adenoma, adrenal cortical carcinoma, adrenal cortical hyperplasia, pheochromocytoma, ganglioneuroma and gangliosarcoma [1, 4]. At present, mainly two clini- cal subsets have been broadly proposed: pre- or sub-clinical Cushing’s syndrome [5-9], and ho- mozygous or heterozygous congenital adrenal hyperplasia [10]. In clinical practice it is possible that these two distinct adrenal cortical adenomas can be excluded on the basis of suppression of the serum cortisol level in 1 mg dexamethasone over- night suppression tests [9] and increase in the se- rum concentration of 17-hydroxyprogesterone [10]. Apart from these two distinct adrenal cortical adenomas, other apparently non-hyperfunctioning adrenal cortical adenomas have remained less in- vestigated [11, 12]. We recently proposed the sig- nificance of steroidogenic enzymes in the patho- genesis of adrenal tumors [13] as well as in adrenal cortical steroid hormone production [14, 15].
In the present study, we examined the steroid content and enzymes involved in the steroidogen- esis of adrenal cortical adenomas resected during gastrectomy or cholecystectomy. This report will further provide data on the characterization of ad- renal incidentaloma.
Patients and Methods
Patients
Ten patients with adrenal non-hyperfunctioning adrenal adenomas were examined. Adrenal glands obtained from three patients with renal cell carci- noma were employed as a control. The adrenal masses were found during pre-operative evalua- tions for gastrectomy or cholecystectomy or exami- nation of the causes of hypertension on CT scans. Before undergoing surgery, the patients were given on explanation of the study protocol and their written consent was obtained. The study pro- tocol was approved by the Ethical Committee of Keio University Hospital [16]. The patients were chosen because 1) there was no evidence of neuro- genic tumor or cyst, 2) there was suppression of the serum cortisol at AM 9:00 by an 1 mg dexamethasone overnight suppression test, and 3) there were negative results following a metoclopramide injection which could reveal oc- cult pheochromocytoma [17].
Endocrine assessment
The clinical and endocrine results for the indi- viduals are summarized in Table 1. All values ob-
| Case | Age | Sex | Blood Pressure | Serum K | Tumor Weight (g) | PRA | PAC | COR | ACTH | 17-OHCS | 17-KS | COR Post DEX | VMA |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 59 | F | 144/90 | 4.2 | 4.1 | 0.06 | 155 | 347 | 4.84 | 10.8 | 8.8 | 65 | 17.66 |
| 2 | 47 | F | 180/100 | 3.8 | 3.8 | 0.06 | 288 | 353 | 2.02 | 16.6 | 16.8 | 74 | 5.05 |
| 3 | 52 | M | 142/92 | 3.8 | 3.1 | 0.12 | 405 | 347 | 2.02 | 21.5 | 32.2 | 82 | 12.62 |
| 4 | 65 | F | 136/88 | 4.5 | 2.5 | 0.14 | 108 | 268 | 2.02 | 12.7 | 35.7 | 54 | 7.06 |
| 5 | 52 | M | 126/78 | 4.4 | 3.8 | 0.14 | 307 | 342 | 2.02 | 22.1 | 33.6 | 96 | 16.15 |
| 6 | 60 | M | 136/80 | 4.2 | 3.2 | 0.18 | 432 | 350 | 2.64 | 21.0 | 39.9 | 70 | 8.07 |
| 7 | 55 | F | 128/66 | 4.0 | 3.8 | 0.14 | 687 | 290 | 3.03 | 25.4 | 37.1 | 64 | 10.6 |
| 8 | 56 | M | 124/78 | 3.9 | 2.8 | 0.31 | 72 | 210 | 2.02 | 23.2 | 36.7 | 80 | 10.1 |
| 9 | 52 | F | 160/72 | 4.5 | 4.0 | 0.24 | 360 | 204 | 6.06 | 20.0 | 33.6 | 59 | 18.67 |
| 10 | 50 | F | 138/72 | 4.5 | 2.9 | 0.28 | 238 | 188 | 11.01 | 22.1 | 31.5 | 69 | 9.59 |
| Mean ± SEM | 55 2 | 141/82 | 4.2 | 3.4 0.2 | 0.17 | 305 | 290 | 3.77 | 19.5 | 30.6 | 67 | 11.56 | |
| 0.8 | 0.03 | 57 | 21 | 0.92 | 1.5 | 3.1 | 2 | 1.46 | |||||
| 5/3 |
Blood Pressure (mmHg); Serum K (mEq/l)(3.8-4.5); PRA, Plasma renin activity (ng/l/s) (0.27-0.48); PAC, Plasma aldo- sterone concentration (pmol/l)(137-685); COR, Plasma cortisol concentration (nmol/l)(138-414); ACTH (pmol/l)(<22.02); 17-OHCS (umol/day)(M:8.3-35.8, F:5.5-19.3); 17-KS (umol/day)(M:14-45.5, F:7-28.0); Post DEX, Dexamethasone 1 mg overnight suppression test COR, <138 nmol/l; VMA, vanillylmandelic acid (mg/day)(<44.0). M: male, F: female, ( )( ), units and normal values, respectively.
tained are within the normal ranges. The aldo- sterone (ALDO) content was measured with an aldosterone RIA kit II (Dainabot Co., Tokyo, Japan). The cortisol content (COR) was estimated with a RIA kit (Baxter y coat- cortisol kit, USA). The plasma renin activity (PRA) was measured by the RIA coated beads method employing a kit from Dainabott Radioisotope Institute, Tokyo, Japan. ACTH was measured by RIA kits from Mitsubishi Yuka Bio-Chemi Lab. Inc., Tokyo. Esti- mations of the urinary 17-OHCS (17-hydro- xycorticosteroids) and 17-KS (17-ketosteroids) were made from the levels of urinary metabolites of the serum adrenocortical hormones. The urinary metabolites were measured by urine hydrolysis with ß-glucuronidase, extraction and colorimetric quantitation employing the Porter-Silver (for 17- OHCS) and Zimmerman (for 17-KS) reactions. The urinary excretion of vanilly mandelic acid (VMA) was estimated by the spectrophotometric determi- nation of vanillin, which was converted from 3- methoxy-4-hydroxymandelic acid (MOMA). MOMA was extracted from the urine with periodate.
Measurement of steroid content in the tumors
The amounts of pregnenolone (PREG), 11- deoxycorticosterone (11-DOC),18-hydroxydeo- xycorticosterone (18-DOC), corticosterone (B), and dehydroepiandrosterone (DHEA) were measured by RIA, with respectively, antisera to PREG-3-suc- cinate-BSA, 11-DOC-3-(O-carboxymethyl) oxime- BSA, B-3-(O-carboxymethyl)oxime-BSA and 11x- succinoyloxy-DHEA-BSA, and preceded by extrac- tion with ether (Teikoku Hormone Mfg., Co., Ltd., Tokyo, Japan). The amounts of 18-DOC were de- termined by RIA with an antiserum to 18-DOC-3- (O-carboxymethyl)oxime-BSA preceded by extrac- tion with dichloromethane (Teikoku Hormone Mfg., Co.). The cortisol content (COR) was mea- sured with a RIA kit (Baxter y coat cortisol kit, USA). The progesterone (PROG) content was esti- mated with another RIA kit (DPC progesterone kit, Japan DPC Co., Tokyo, Japan). The aldosterone (ALDO) content was measured with an aldo- sterone RIA kit II (Dainabot Co., Tokyo, Japan).
Measurement of enzyme activities
Mitochondrial and microsomal fractions were
obtained from the tumor and the adjacent portions of the adrenals of all patients and from the control adrenals by differential centrifugation [18].
P-450scc activity assay : The mitochondrial frac- tion (30 µg of protein) was disrupted by freezing and thawing. In a reconstituted enzyme system in- cluding 111 umol/l 20a-hydroxycholesterol as a substrate, 14 umol/l adrenodoxin (purified from the bovine adrenals by ourselves) and 0.3 umol/l NADPH-adrenodoxin reductase (purified from the bovine adrenals by ourselves) as an electron trans- fer system, 5 mmol/l isocitrate, 0.4 units isocitrate dehydrogenase per ml, and 5 mmol/l isocitrate, 0.4 units isocitrate dehydrogenase per ml, and 5 mmol/l MgCl2 as an NADPH-generating system were dissolved in 20 mmol/l potassium phosphate buffer (pH 7.4) and 0.3% Tween 20. The reaction was initiated by adding NADPH, and was termi- nated by adding 10% cholic acid. The product, pregnenolone, was converted to progesterone by adding cholesterol oxidase, and the final product was extracted with dichloromethane and analyzed by HPLC on a TSK gel silica 150 column (4.6×250 mm; Tosoh, Tokyo, Japan) with n-hexane : isopropanol (100 : 2) as the mobile phase [19]. The HPLC system consisted of a Trirotor II pump and a Uvidec-100-III detector (Jasco, Tokyo, Japan). We used 5 nmol of DOCA as the internal standard.
P-450118 activity assay: The mitochondrial frac- tion (30 µg of protein) was disrupted by freezing and thawing. In a reconstituted enzyme system in- cluding 100 umol/l DOC as a substrate, 14 umol/l adrenodoxin, 0.3 umol/l NADPH-adrenodoxin re- ductase as an electron transport system, 5 mmol/l isocitrate, 0.4 units of isocitrate dehydrogenase per ml and 5 mmol/l MgCl2 as an NADPH-generating system were dissolved in 100 mmol/l potassium phosphate buffer (pH 7.4) and 0.1 mmol/l EDTA. The reaction was initiated by adding NADPH, and was terminated by adding dichloromethane. The reaction product was extracted with dichlo- romethane and analyzed by HPLC on a TSK gel silica 150 column with dichloromethane: ethanol : water (96 : 3.6 : 0.4) as the mobile phase [20, 21].
P-45017a and P-450C21 activity assay: The mi- crosomal fraction (30 µg of protein) was reacted with 100 umol/l progesterone as a substrate, 5 mmol/l isocitrate, 0.4 units of isocitrate dehydro- genase per ml, and 5 mmol/l MgCl2 as an NADPH-generating system, resolving into 100 mmol/l potassium phosphate buffer (pH 7.4) and
0.1 mmol/l EDTA. The reaction was initiated by adding NADPH, and was terminated by adding dichloromethane. The reaction product was ex- tracted with dichloromethane and analyzed by HPLC on a TSK gel silica 150 column with n- hexane:isopropanol:acetate (93 : 7 : 1) as the mobile phase [22]. We used 10 nmol of spironolactone as the internal standard.
Immunoblot analysis
Sodium dodecyl sulfate-polyacrylamide gel elec- trophoresis of mitochondrial and microsomal ly- sates obtained from human adrenal tumors was carried out on 7.5% gel according to Laemmli’s method [23]. Immunoblotting onto polyvinylidene difluoride membranes was performed as described previously [24]. The membrane for each tumor was blocked with skimmed milk, and incubated with anti-bovine P-450scc, anti-bovine P-450118, anti-por- cine P-45017a or anti-bovine P-450C21 IgG (the anti- bovine P-450118 IgG was a generous gift from Dr. F. Mitani, Department of Biochemistry, Keio Univer- sity and the other antibodies were purchased from OXY gene DALLAS, U.S.A.). The materials were then reacted with anti-rabbit IgG-biotin complex and visualized by reaction with diaminobenzidine [25].
Statistical analysis
The results are expressed as the means + SEM. Statistical analysis was performed by Wilcoxon Signed-Rank for paired t-test and Mann-Whitney U for unpaired t-test. Significance was set at P<0.05.
Results
Steroid contents of non-hyperfunctioning adrenal adenomas
The steroid contents of the adrenal tumors from 5 of the 10 patients (cases 1 to 5) were examined and the data are shown in Table 2. Even though the control values were obtained from the appar- ently normal adrenals of patients with renal cell carcinoma, no abnormal or distinctive values were observed among the non-hyperfunctioning adrenal adenomas except for aldosterone which were lower than for the apparently normal adrenals.
Steroidogenic P-450 activities and amounts
The expressed amounts and activities of P-450scc, P-450118, P-450aldo, P-45017% and P-450c21 in the tu- mor and adjacent portions of the non-hyperfunc- tioning tumors from 5 of the 10 patients (cases 6 to 10) were found to be similar to those in the normal control adrenals (Fig. 1 and Table 3). However, the expressed amounts and activities of both P-450g and P-45017a in the tumor portion were signifi- cantly greater than those in the adjacent portion.
Histology
In all 10 patients, grossly well-demarcated yel- lowish-brown tumors of the adrenal gland were seen. Microscopically, these tumors were sur- rounded by a thin, non-intact capsule. The adjacent portion of tumors was not atrophic and apparently normal. The cells of both the tumor and adjacent
| Case | ALDO | 11-DOC | 18-DOC | B | COR | DHEA | PREG | PROG |
|---|---|---|---|---|---|---|---|---|
| 1 | 27.7 | 101 | 159 | 19.7 | 60.6 | 801 | 6.23 | 3282 |
| 2 | 60.9 | 10 | 371 | 28.8 | 13.8 | 1381 | 1.82 | 7488 |
| 3 | 60.9 | 151 | 505 | 38.9 | 137.9 | 464 | 4.65 | 4364 |
| 4 | 69.3 | 91 | 307 | 34.7 | 60.6 | 1037 | 5.00 | 5887 |
| 5 | 160.6 | 68 | 424 | 25.9 | 22.0 | 864 | 1.82 | 6386 |
| Mean | 75.8 | 84 | 353 | 29.8 | 59.2 | 909 | 3.90 | 5481 |
| ± SEM | 22.5 | 23 | 58 | 3.3 | 21.9 | 150 | 0.89 | 744 |
ALDO, aldosterone (pmol)(153.4+10.9); 11-DOC, 11-deoxycorticosterone (pmol)(212+107); 18-DOC, 18-hydro- xydeoxycorticosterone (pmol)(347+33); B, corticosterone (nmol)(18.6+9.8); COR, cortisol (nmol)(49.5±5.4); DHEA, dehydroxyoepiandrosterone (pmol)(1051+239); PREG, pregnenolone, (nmol)(3.85+0.56), PROG, proges- terone (pmol)(13979+4092). ()(), unit and normal values, respectively
P-450scc
-
4 51K
P-45011
50K
P-45017a
55K
P-450C21
47K
1 2 Normal
12345 Non-hyperfunctioning
portions were arranged in nets and cords. No nuclear atypia or mitosis was observed.
Discussion
In the present study, apparently non-hyperfunc- tioning adrenal cortical adenomas produced adre- nal steroids and these were probably regulated by steroidogenic enzymes. Further, in the adrenal tis- sue containing the non-hyperfunctioning adrenal cortical adenoma, the adjacent portion was not atrophic and also had steroidogenic enzymes. These data suggest that non-hyperfunctioning ad- renal cortical adenomas are completely different from hyperfunctioning adenomas. Recently, we proposed the significance of steroidogenic en- zymes in the pathogenesis of adrenal tumors [13]. In the adrenal mitochondria of patients with pri- mary aldosteronism, both the activities and amounts of steroidogenic cytochrome P-450aldo were significantly increased, and in those of pa- tients with Cushing’s syndrome, the P-45017a and P-450(21 levels were significantly increased. More- over, such increases were found only in the tumor portion and not in the adjacent portion. Similar findings have been obtained by Ogo et al. [26, 27] who reported that expression of the steroidogenic P-450 mRNAs was increased in patients with pri- mary aldosteronism and with Cushing’s syn- drome. Further, Sasano et al. [28-30] demonstrated immunohistochemically that the P-450118 immu- noreactivity was intense in patients with primary aldosteronism and the P-45017a immunoreactivity was intense in patients with Cushing’s syndrome. Conversely, a high incidence of adrenal adenomas
| Case | P-450 scc | P-450118 | P-450aldo | P-45017a | P-450C21 |
|---|---|---|---|---|---|
| 6 | 7.39 | 2.20 | <3 | 8.40 | 7.06 |
| 7 | 7.91 | 3.00 | <3 | 5.14 | 1.80 |
| 8 | 6.21 | 1.20 | <3 | 2.31 | 3.04 |
| 9 | 5.42 | 0.80 | <3 | 4.39 | 2.80 |
| 10 | 4.40 | 1.80 | <3 | 7.69 | 2.04 |
| Mean | 6.26 | 1.80 | <3 | 5.57 | 3.35 |
| ±SEM | 0.64 | 0.39 | 1.11 | 0.69 |
P-450scc (nmol/min/mg protein) (6.03+2.03); P-450118 (nmol/min/mg protein) (1.94+0.59); P-450aldo (pmol/min/mg protein) (<3); P-45017a (nmol/min/mg protein) (4.25+0.87); P-450C21(nmol/min/mg protein) (4.32+0.57). ()(), unit and normal values, respectively.
| Case | P-450sco | P-45011B | P-450aldo | P-45017a | P-450c21 |
|---|---|---|---|---|---|
| 6 | 6.20 | 1.40 | <3 | 3.68 | 6.50 |
| 7 | 4.69 | 1.50 | <3 | 2.91 | 1.20 |
| 8 | 4.80 | 2.40 | <3 | 2.18 | 2.80 |
| 9 | 4.46 | 1.80 | <3 | 4.42 | 2.20 |
| 10 | 3.94 | 1.10 | <3 | 1.22 | 1.56 |
| Mean | 4.82 | 1.64 | <3 | 2.88 | 2.85 |
| ±SEM | 0.37 | 0.22 | 0.56 | 0.95 |
P-450scc (nmol/min/mg protein)(6.03+2.03); P-450118 (nmol/min/mg protein)(1.94+0.59); P-450aldo (pmol/min/mg protein)(<3); P-45017a (nmol/min/mg protein)(4.25±0.87); P-450C21 (nmol/min/mg protein)(4.32+0.57). ()(), unit and normal values, respectively.
has been found in heterozygous and homozygous patients with congenital adrenal hyperplasia [10]. In view of results, it seems likely that abnormali- ties of steroidogenic cytochrome P-450s may play a role in hyperfunctioning adrenal cortical adenomas.
Along similar lines to these investigations, sev- eral recent studies on incidentalomas have been conducted on patients with preclinical Cushing’s syndrome, congenital adrenal hyperplasia and non-hyperfunctioning adrenal cortical adenoma [12]. The entity termed pre-Cushing’s syndrome, sub-clinical Cushing’s syndrome or preclinical Cushing’s syndrome has been proposed by several investigators [5-9]. The prevalence of this syn- drome has been reported to be relatively high, ac- counting for about 5 to 12% of all adrenal incidentalomas. It was suggested that the best screening test for preclinical Cushing’s syndrome in patients with an incidentally discovered mass is the low dose dexamethasone test. In all 10 patients in the present study, low dose dexamethasone test was carried out and yielded negative results. Fur- ther histological examinations of the adjacent por- tion of preclinical Cushing’s syndrome have re- vealed it to be at least atrophic. These findings are in striking contrast to the present data. In our study, the adjacent portion in all 10 patients was not at all atrophic in appearance. Another possible non-hyperfunctioning adrenal cortical adenoma is related to patients with homozygous and heterozy- gous congenital adrenal hyperplasia. However, in the present study, cytochrome P-450C21 was de- tected in all patients. It seems unlikely therefore that in any of the patients examined in the present study, the cortical adenoma could be diagnosed as congenital adrenal hyperplasia.
There have been few reports on the steroid con- tents and steroidogenic enzymes in cases of non- hyperfunctioning adrenal cortical adenoma [11, 12]. One major reason is probably due to its hetero- geneity. In the present study, we excluded metastasis, cyst, lipoma, and ganglioneuroma by means of CT scan and MR images, and also ruled out adrenal cortical carcinoma histologically. Fukushima & Gallagher [31] first reported that “non-functional” adrenocortical adenoma was able to produce pregnenolone and progesterone. Kaplan et al. [32] examined the steroids in adrenal adenomas from patients with essential hyperten- sion. They demonstrated that the amounts of aldo- sterone and corticosterone in these patients were similar to those in normal adrenal tissue and much less than in adenomas from patients with primary aldosteronism. Recently, Gröndal et al. [11] exam- ined the basal and ACTH-stimulated cortisol and aldosterone release from adrenocortical adenoma of patients with primary aldosteronism, Cushing’s syndrome and non-hyperfunctioning adenoma. In their study, no conclusive data were obtained be- cause of the varied histologic appearance of non- hyperfunctioning adrenal cortical adenomas. Two cases which may be similar to our cases showed that ACTH increased the cortisol release to the same extent as in the cortex. In the present study, since all steroidogenic enzymes are found in the tumor and adjacent portions, it is possible that even non-hyperfunctioning adrenal cortical adenoma may respond to the stimuli. Recently, Ogo et al. [12] have observed the expression of ad- renal steroidogenic P-450 mRNA in non-hyper- functioning adrenal cortical adenoma and they were not different from those in the normal adre- nal gland. These data are essentially similar to our
present data obtained from the protein levels of steroidogenic P-450s. In the present study, al- though we did not measure the steroids in the por- tions adjacent to non-hyperfunctioning tumors, there were some differences in enzyme activities between the tumor and portions adjacent to non- hyperfunctioning tumors. Both P-450scc and P- 45017a in particular were greater in the tumor por- tion than in the adjacent portions. In our previous results on adrenal tumors from patients with Cushing’s syndrome, the activities of P-45017« in- creased [13]. Moreover, the amount of aldosterone in the tumor portion was much smaller. Taken together, these data suggest that the shift in ste- roidogenesis from the 17-deoxypathway to the 17- hydroxypathway occurs in some non-hyperfunc- tioning tumors. Or some of these tumor may de- velop pre-Cushing’s syndrome.
In previous studies, we proposed a possible role of abnormal expression of steroidogenic enzymes in the pathogenesis of hyperfunctioning adrenal tumors [13]. Compared to these findings, the tumorigenesis of non-hyperfunctioning adrenal adenomas might be the result of factors other than steroidogenic enzymes. Since we were unable to elucidate the factors contributing the non-hyper-
functioning adrenal adenomas in the present study, further detailed research needs to be under- taken. Moreover, in the present study, elevation of blood pressure in some cases (Cases 2 and 9) be- fore surgery failed to decrease after operation. It is therefore suggested that non-hyperfunctioning ad- renal adenoma did not affect blood pressure levels as well as other signs and symptoms.
As far as the operability of these tumors is con- cerned, no clear-cut standards for adrenalectomy have yet been put forward for cases suspected of being malignant tumors. The tumors which were examined in the present study were obtained dur- ing other major surgery such as gastrectomy or cholecystectomy. Based on the steroid content and histological features, all of the tumors were benign.
In conclusion, this report is the first to demon- strate that some non-hyperfunctioning adrenal cor- tical adenomas can produce adrenal steroids and contain steroidogenic enzymes, although it still re- mains undetermined whether these are normally functioning or not. In addition, decrease in aldo- sterone content and increase in P-45017g activities suggest a shift of steroidogenesis from a mineralo- corticoid pathway to a glucocorticoid pathway in non-hyperfunctioning tumor.
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