Adrenocortical Function in Old Age: Response to Acute Adrenocorticotropin Stimulation*
A. VERMEULEN, J. P. DESLYPERE, W. SCHELFHOUT, L. VERDONCK, AND R. RUBENS
Section of Endocrinology, and the Department of Urology (W.S.), Academic Hospital, University School of Medicine, B 9000 Ghent, Belgium
ABSTRACT. To elucidate the controversial point whether, in analogy with 45-steroid secretion, adrenal 44-steroid secretion is significantly decreased in elderly persons, we studied the re- sponse of plasma levels of both 45-steroids (dehydroepiandros- terone, 17-hydroxypregnenolone, and pregnenolone) and 44-ste- roids (cortisol, androstenedione, 17-hydroxyprogesterone, and progesterone) to acute ACTH stimulation in four groups of young and elderly males and females, respectively. To study the possible influence of sex hormones on adrenocortical function in elderly persons, we performed the same study in males with
prostatic carcinoma treated with estrogens. The data show that in elderly persons, the response of plasma 44-steroids to ACTH stimulation is comparable or higher than that in young subjects, whereas the response of 45-steroids is significantly decreased; estrogen treatment does not change this pattern. It is concluded that in elderly persons adrenal 44-steroid secretory capacity is unimpaired, whereas 45-steroid secretion is significantly de- creased. The responsible mechanism remains to be elucidated. (J Clin Endocrinol Metab 54: 187, 1982)
I N POSTMENOPAUSAL women, the adrenal cortex is the almost exclusive source of plasma sex hor- mones, except for testosterone (1, 2). It is, moreover, generally admitted that in both sexes, adrenocortical secretion of dehydroepiandrosterone (D) and its sulfate (DS) decreases with age (3-5), but whether adrenal an- drostenedione (A) and, more generally, 44-steroid secre- tion decrease with age is still controversial (5-10). Yet, in as far as in postmenopausal women A is the major precursor of plasma estrogens, which play an important role in the prevention of menopausal pathology, such as osteoporosis, or in the genesis of endometrial cancer, it is important to know the factors that influence adrenocor- tical secretion of A and of 44-steroids in general.
To gain a better insight into the influence of age on adrenocortical function, we studied in both sexes the influence of age on the response to acute ACTH stimu- lation of A plasma levels, as well as of its immediate biosynthetic precursors, 17-hydroxyprogesterone (17OHP) and progesterone (P), and of dehydroepian- drosterone (D) and its precursors 17-hydroxy-pregn-5- ene-33-ol-20-one [17-hydroxypregnenolone (170HP5)] and pregn-5-en-38-ol-20-one [pregnenolone (P5)]. More- over, we studied the influence of estrogens on adrenal
Address requests for reprints to: Prof. A. Vermeulen, Section of Endocrinology, Academic Hospital, University School of Medicine, B 9000 Ghent, Belgium.
* This work was supported by Grant 3.0014.78 from the NFWO.
secretion by comparing the response to ACTH obtained in elderly males with prostatic carcinoma treated with estrogens to the response in a comparable untreated group.
Materials and Methods
Subjects
The ACTH test was performed in 4 groups (young and elderly males and females, respectively) consisting of 6-12 sub- jects each. All subjects tested were within 10% of ideal body weight.
Women of reproductive age (22-43 yr; mean age, 28 yr) were studied during the early follicular phase of the cycle (days 3-8); they were student volunteers or paramedical personnel. Elderly women, 54-77 yr old (mean age, 62 yr), were in spontaneous postmenopause. All were in general good health and had not taken any contraceptive or other hormonal preparation in the last year.
The group of young males consisted of collaborators, 18-39 yr old (mean age, 33 yr); the elderly subjects were 51-89 yr old (mean age, 68 yr) and in general good health.
An ACTH stimulation test was also performed in a group (n = 5) of elderly males (>60 yr old) with prostatic cancer, treated for several months with estrogens (2-3 mg diethylstilbestrol daily). For comparison of basal levels, hormone levels before estrogen treatment as well as levels in a group of orchidecto- mized males are also presented.
The ACTH stimulation test was performed using the syn- thetic 1-24 analog Synacthen (0.25 mg, iv). Blood samples were
taken via an indwelling catheter 20 min before and 0, 30, 60, 90, and 120 min after injection; all tests were started between 0800- 1000 h. The basal values given are concentrations at zero time which, due to the transient stress of vein puncture, were slightly lower than concentrations 20 min before injection.
Plasma hormone levels
A, D, DS, P, and 17OHP were measured using RIA methods previously described (5, 11).
Ps and 170HP5 were measured by RIA using antibodies obtained by immunization of rabbits with the respective 3- hemisuccinate-bovine serum albumin complex. Before RIA, the ether extract of the plasma sample was purified by thin layer chromatography (TLC) of silica gel in the system chloroform- aceton (85:15, vol/vol).
As far as specificity of the 17OHPs antibody is concerned, the highest cross-reaction was observed with 17aOHP (2.5%); all other hormones occurring in plasma showed a cross-reaction of less than 0.1%. The sensitivity of the 170HP, RIA was 20 pg/sample, the coefficient of variation at a concentration of 100 ng/dl was 10.7%, and the mean recovery at the same concentra- tion was 98 ± 7%.
The Ps antibody cross-reacted 18% with 170HP5; however, the latter was separated from Ps by TLC; other plasma steroids cross-reacted less than 0.1%. The sensitivity of the RIA was 20 pg/sample; the coefficient of variation at 50 ng/dl was 7.6%; recovery was 104 ± 9%.
Normal values for both P5 and 170HP, in males and females were in the range of those previously reported (see Results) (12-18).
Results were analyzed by the two-tailed Mann-Whitney U nonparametric test.
Results
Basal adrenal hormone levels in the different groups studied are represented in Table 1, whereas the increase over basal levels after ACTH stimulation, in both men and women is represented in Figs. 1 and 2.
With the exception of cortisol (F) and of P in males, the basal levels of all steroids studied were lower in elderly persons of either sex than in younger adults. After ACTH stimulation, the increase over basal levels of all 44-steroids (F, A, P, and 17OHP) in elderly persons was similar or higher than the increase in young persons; for all 45-steroids, on the other hand (D, P5, and 170HP5), the increase in elderly males and females was lower than that in young persons. The same pattern applied to the
absolute plasma levels reached.
The smaller increase over basal levels of 45-steroids in elderly persons became even more significant (P < 0.02 for all points) when the groups of young males and females as well as elderly males and females were pooled. This was justified, since for all steroids studied after ACTH stimulation, the increases over basal levels were similar in both sexes.
The temporal patterns of the rise of adrenal hormones, on the other hand, were similar in young and elderly persons for 45- as well as for 44-steroids. In elderly males with prostatic carcinoma treated with estrogens, ACTH stimulation gave similar results; 44-steroid levels were higher than those observed in young males, and 45-ste- roid levels remained significantly below levels observed in young males (Table 2).
Moreover, it could be seen that estrogen treatment did not influence basal adrenocortical hormone levels (Table 3).
Discussion
In both elderly males and females, plasma levels of 45- steroids are considered to have essentially an adrenal origin, with only a minor gonadal contribution (19-21); the important decrease with age in their plasma levels, therefore, certainly reflects decreased adrenal secretion. As for the 44-steroids, in males, A as well as P levels have a predominant adrenal origin (11, 22, 23), whereas in women, the ovarian contribution to A levels during early follicular phase is about one third and to P levels about half (20, 21). The same applies to 170HP levels, which in both sexes originate both from the gonads and adrenals (11, 21, 23-25). Hence, the relative role of gonads and adrenals in the age-associated decrease in the basal plasma levels of these steroids is difficult to evaluate.
Our data after ACTH stimulation, however, show that the influence of age on adrenal steroid secretion is quite different when 45- or 44-steroids are concerned. Indeed, the basal levels, the absolute levels reached, and the increase over basal levels after ACTH stimulation of all 45-steroids are significantly lower in both elderly men and women, whereas for 44-steroids, the response to ACTH stimulation in elderly persons is unchanged or even increased in comparison to the response in young subjects. Whether the increased levels reflect increased
| F | P | 170HP | A | P5 | 170HP5 | D | |
|---|---|---|---|---|---|---|---|
| Young women | 190 ± 20 | 38 ± 7 | 51 ± 15 | 152 ± 9 | 72 ± 9 | 153 ± 40 | 517 ± 115 |
| MP women | 170 ± 20 | 22 ± 3 | 34 ± 8 | 84 ± 14 | 40 ± 17 | 26 ± 9 | 94 ± 19 |
| Young men | 160 ± 10 | 11 ± 3 | 101 ± 22 | 107 ± 9 | 56 ± 7 | 164 ± 21 | 269 ± 45 |
| Elderly men | 150 ± 20 | 11 ± 2 | 82 ± 17 | 97 ± 19 | 39 ± 13 | 93 ± 34 | 155 ± 35 |
Mp, postmenopausal women.
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400 ng/ml
E
F
300.
İ
Y
200.
Y
MP
100.
17OHP
3
MP
2
E
1
1
Y
Y
P
2.0
MP
1.6.
1.2.
E
0.8.
0.4.
Y
Y
A
0.2.
MP
E
0.8.
0.4
1
Y
Y
30
60
90
120
30
60
90
120
secretion or are a consequence of an age-associated de- crease in the MCR remains to be determined. The age independency of adrenal 44-steroids is in agreement with the well known age independency of plasma cortisol and 11-hydroxyandrostenedione (26) and with data from this (27) and some other laboratories (6, 8, 9, 28) suggesting that A levels do not decrease with age in either postmen- opausal women or elderly males and that P levels do not decrease in elderly males (11). Recently Longcope et al. (29) reported the blood production rate of A in postmen- opausal women to be independent of age. It should be mentioned, nevertheless, that Roger et al. (7) did report an age-dependent decrease in A levels in postmenopausal women, whereas Pirke et al. (23) observed a similar decrease in males. Assuming eventual changes in the MCR of 44-steroids to parallel those of 45-steriods, the total adrenal steroid output after ACTH stimulation
Ở
17OHP5
ㅎ
Y
8
ng/ml
6
Y
4.
2
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I
1
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Î
E
MP
P5
Y
1.5
Y
1.0
0.5
1
1
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8
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4.
2.
1
E
1
1
MP
30
60
90
120
30
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seems to be decreased in elderly compared to young persons, as the eventually slightly increased response of 44-steroids does not compensate for the decrease in the quantitatively more important 45-steroid secretion. The mechanism of this selectively age-dependent decrease in adrenal 45-steroid levels remains to be elucidated. A selective increase in the MCRs of the 45-steroids is unlikely, whereas it is improbable that the decreased gonadal sex hormone secretion in elderly subjects deter- mines the decreased adrenal secretion of 45-steroids. Indeed, in castrated males, adrenal hormone levels are only slightly lower than in normal males of similar age. Similarly, decreased estrogen levels, suggested to be re- sponsible for the decreased D and DS secretion in post- menopausal women (30), probably do not play a role; indeed, in elderly males, estrogen levels are similar or increased compared to levels in younger males, while estrogen treatment of patients with prostatic carcinoma influenced neither basal nor ACTH-stimulated adrenal androgen levels. This confirms the negative findings ob- served by some investigators (31-34). It is also unlikely that the increased gonadotropin levels found in elderly persons would play a role in the age-dependent changes of adrenal androgen secretion; indeed, our results show that gonadectomy in males, although inducing highly increased gonadotropin levels, does not influence adrenal androgen levels.
A role for PRL in the adrenal aging process is similarly
| Estrogen-treated males (n = 5) | Normal young males (n = 10) | |||||||
|---|---|---|---|---|---|---|---|---|
| Basal | 30 min | 60 min | 120 min | Basal | 30 min | 60 min | 120 min | |
| A | 81 ± 17 | 210 ± 16 | 270 ± 32 | 228 ± 21 | 107 ± 9 | 158 ± 16 | 155 ± 19 | 177 ± 19 |
| 170HP | 34 ± 8 | 351 ± 21 | 326 ± 15 | 235 ± 26 | 101 ± 22 | 159 ± 20 | 177 ± 19 | 150 ± 16 |
| P | 12± 3 | 164 ± 5 | 159 ± 22 | 133 ± 40 | 11 ± 3 | 55 ± 11 | 63 ± 9 | 58 ± 6 |
| D | 152 ± 16 | 436 ± 68 | 532 ± 71 | 495 ± 42 | 269 ± 45 | 740 ± 106 | 751 ± 104 | 869 ± 98 |
| 170HP5 | 29 ± 5 | 264 ± 38 | 287 ± 25 | 323 ± 14 | 164 ± 21 | 536 ± 97 | 592 ± 109 | 582 ± 84 |
| P5 | 31 ± 7 | 106 ± 28 | 105 ± 21 | 134 ± 18 | 56 ± 7 | 131 ± 10 | 140 ± 14 | 145 ± 16 |
| T (ng/dl) | D (ng/dl) | DS (µg/dl) | A (ng/dl) | P (ng/dl) | 170HP (ng/ dl) | P5 (ng/dl) | 170HPs (ng/ dl) | |
|---|---|---|---|---|---|---|---|---|
| Before treatment | 587 ± 14 26 ± 5 | 192 ± 31 170 ± 25 | 50 ± 14 51 ± 8 | 99 ± 18 87 ± 13 | 21 ± 2 19 ± 1 | 90 ± 8 33 ± 3 | 54 ± 10 34 ± 10 | 80 ± 13 50 ± 12 |
| During estrogen treatment | ||||||||
| Orchidectomized males (60-80 yr; n = 28) | 19 ± 4 | 142 ± 21 | 53 ± 10 | 92 ± 26 | 18 ± 4 | 34 ± 4 | 28 ± 3 | 66 ± 13 |
T, Testosterone.
unlikely, as in elderly males, PRL levels are higher, but in postmenopausal women are slightly lower than during reproductive life.
Finally, there is no experimental evidence for a de- creased cortisol flux from the zona fasciculata to the zona reticularis in aging subjects, a mechanism suggested by Anderson (35) to influence adrenal androgen secretion. As to a possible role of the hypothetical androgen-stim- ulating hormone (36), we have to await its further iden- tification.
Whatever the mechanism may be, our data show clearly the decreased adrenal secretion and response to acute ACTH stimulation of all 45-steroids, with preser- vation of 44-steroid secretion, in both aging males and females, independent of sex hormone (estrogen) or go- nadotropin levels.
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