Clinical Endocrinology ( 1 979) 11,475-479
FAILURE O F NALOXONE T O ALTER GROWTH H O R M O N E AND PROLACTIN LEVELS IN ACROMEGALIC A N D I N HYPERPROLACTINAEMIC PATIENTS J . BLANKSTEIN,* F. REYES, J . WINTER
AND
C . FAIMAN
Departments of Obstetrics and Gynaecology. Physiology, Paediatrics and Medicine, University of Manitoba and the Endocrine- Metabolism Laboratory , Health Sciences Centre, Winnipeg, Manitoba, Canada, R3E 0 2 3 (Received 26 February 1979; reui.red 10 May 1979; accepted 10 May 1979)
SUMMARY
We examined the effects of high-dose intravenous naloxone administration in four acromegalic patients (mean serum growth hormone level 72 ng/ml) and in seven hyperprolactinaemic women (mean serum prolactin level 59 ng/ml), in order to assess whether this opiate antagonist would be effective in lowering growth hormone and prolactin levels. No effect was observed. This lack of effect suggests that an opioid pathway is not involved in the maintenance of elevated growth hormone or prolactin secretion in these patients. However, conclusions regarding the possible role of endogenous opioids in regulation of pituitary function in normal individuals cannot be drawn from this study. The discoveries of opiate receptors in the human central nervous system (Pert & Snyder, 1973) and of endorphins, a group of endogenous substances with opiate-like activity (Goldstein, 1976), have suggested that the latter may function as neurotransmitters capable of influencing those pituitary functions which are known to be affected by exogenous opiates. Thus, it has been shown that administration of morphine results in significant increases of serum growth hormone and prolactin in rats (Rivier et al., 1977; Bruni et al., 1977) and of prolactin in primates, including man (Gold et al., 1978; Tolis et al., 1975). Two recent reports have described a stimulatory effect of an enkephalin analogue upon prolactin and growth hormone secretion in healthy men (Stubbs et al., 1978; von Graffenried el al., 1978). In one of these studies (Stubbs er al., 1978), prior administration of a pure antagonist of opiate action, naloxone, in a dose of 0.4 mg, attenuated the response of both prolactin and growth hormone. The aim of the present study was to assess whether high doses of naloxone would be effective in lowering growth hormone and prolactin levels in acromegalic and hyperprolactinaemic patients. Present address: Department of Obstetrics and Gynaecology, Tel Hashomer Hospital, Israel. Correspondence: Dr. Charles Faiman, (3449-Health Sciences Centre, Department of Endocrinology and Metabolism, 700 William Avenue, Winnipeg, Manitoba, Canada R3E 023.
0300-0664/79/1100-0475W2.00
0 1979 Blackwell Scientific Publications 475
416
J . Blanksteiri et al. PATIENTS A N D METHODS
Four acromegalic patients ranging in age from 34-64 years, and seven hyperprolact inaemic women ranging in age from 20-36 volunteered for this study. The mean serum growth hormone level in the acromegalic group was 72 ng/ml (range 9-220 ng/ml) and the mean serum prolactin level in the hyperprolactinaemic group was 59 ng/ml (range 22-95 ngiml). Pituitary tumours were documented by hypocycloidal sellar tomography (Vezina & Sutton, 1974) in all of the acromegalic and in one of the hyperprolactinaemic patients; the remaining hyperprolactinaemic women did not show signsof a pituitary tumour and were considered dysfunctional (Gomez et al., 1977). The patients reported to the laboratory at 08.00 h and rested for 1 hour. Then a slow intravenous infusion was started, through which 8 ml samples of blood were withdrawn every 15 min over 1 hour. At the beginning of the second hour, naloxone (Endo Laboratories, Garden City, New York supplied in 1 mg/ml and 10 mg/ml ampoules in saline) was infused. The hyperprolactinaemic group received the naloxone by means of a Harvard pump, which delivered 2.3 mg in the first I 5 min, and then 4.5, 1 1 and 23 mg i n each subsequent I5 min period. The total amount infused was 40.8 mg. The acromegalic patients received a bolus of 10 mg in one ml at the beginning of the second hour. During the second hour, blood samples were taken every 5 min in the hyperprolactinaemic group and every 15 min in the acromegalic group. In the third hour blood samples were taken every 15 min. Blood pressure and pulse rate were measured every 10 min throughout the experiment. In four of the hyperprolactinaemic patients and in all acromegalic patients a separate control study was also performed 3 4 weeks later using the same protocol with infusion of identical volumes of saline vehicle only. Measurements of serum prolactin and growth hormone were performed by previously described radioimmunoassay techniques (Hwang el al., 1971; Morgan, 1966). The significance of differences in hormone concentrations between the naloxone- and saline-infused groups, and of pre- versus post-treatment mean levels was assessed by analysis of variance using a mixed factorial design programme (Becker & Chebib, 1969).
RESULTS Prolactin Mean prolactin levels in response to naloxone (40.8 mg) and saline vehicle are shown in Fig. 1. In both groups there was a significant decrease in mean prolactin levels during and after the infusion. However, there was no significant difference between the two groups. Growth Hormone The response to naloxone (10 mg) and saline bolus in four acromegalic patients are shown in Fig. 2. In three patients there were n o significant changes in growth hormone levels following naloxone or saline vehicle administration. In one patient (LN), there was a decline in growth hormone concentrations following naloxone, but a similar response was also obtained following saline injection. Overall, there was no significant difference between pre- and post-naloxone growth hormone levels and between the naloxone and the control growth hormone response. Blood pressure and pulse rate did not change significantly in any of the individuals
Naloxone in acromegaly and hyperprolactinaernia
477
Infusion
-
8- -.--a
E
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,.\ \.' '. ,.-.
FT
8-J2\.1..8,,y, ,a Ra. 0'
._ 60 -+=8". 0 L
y
/ \ . , * a
; a
5 50-
- 60
soline(,,=4)
\
\
\
@\
'
8'
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I-
*-'.
50
\./*\./Noloxone
a L l ln
(n-7) I
I
I
I
I
I
40
I
260
0
I W
40 -
20 -
5-
I
I
-30 0
I
I
60
I
I
I
I
I
120
I
-30 0
1
I
60
1
I
I
l
120
Time (min)
Fig. 2. Effect of naloxone (solid line) and saline (broken line) o n growth hormone levels in four acromegalic patients. Naloxone (10 mg) or saline vehicle were administered at time 0 (arrows).
following drug or vehicle administration. No psychological or neurological effects were observed throughout the experiment.
DISCUSSION Growth hormone and prolactin levels have been found to increase significantly following administration of morphine and met-enkephalin in the rat; naloxone, an opiate antagonist with virtually n o agonist properties (Martin, 1967), lowered serum growth hormone and prolactin levels (Rivier et al., 1977; Bruni et al., 1977), an observation which suggested that in this species endorphins may participate in the regulation of secretion of these hormones. Morphine also increases serum prolactin levels in monkeys (Gold et al.,
478
J . Blankstein
el
al.
1978) and in man (Tolis et al., 1975). Moreover, synthetic enkephalin analogues were found to have a stimulatory effect on the secretion of growth hormone and prolactin in man (Stubbs et al., 1978; von Graffenried et a/., 1978). Thus one might have expected a naloxone-induced decline in growth hormone and prolactin levels if endogenous opioids were involved in the maintenance of elevated serum levels in pathological conditions. The failure to observe such an effect in acromegalic and hyperprolactinaemic patients would suggest that an opioid pathway is not involved, provided that the amount of naloxone administered (10-40 mg) was sufficient to saturate opioid receptors. This dose of naloxone is 25-100 times higher than the usual adult dose of 0.4 mg used in treating narcotic overdoses, which makes the possibility of failure to fully occupy potential endorphin receptors seem very remote. It is possible that in the acromegalic group and in at least one of the hyperprolactinaemic patients, the lack of response is due to the presence of an autonomously functioning pituitary neoplasm. However, n o neoplasms were detected in six of the latter group, and in these the hyperprolactinaemia is felt to be dysfunctional (Gomez el a / . , 1977). It should be emphasized that the failure of this therapeutic trial in these pathological conditions does not preclude the possibility that endogenous opioids play a role in the physiological regulation of growth hormone and prolactin secretion in man. ACKNOWLEDGEMENTS
Supported in part by the Medical Research Council of Canada (Grant PG-5). The authors wish to thank Dr N. Gupta, Endo Pharmaceuticals, for the kind gift of naloxone. Dr H . G. Friesen, University of Manitoba, for providing the prolactin assay reagents, Dr F. S. Chebib, for helpful statistical advise, M r R. Graham, Ms J . Schilling and Mrs M . Auringer, R. N., for technical assistanceand Ms L. lnsull and Ms J . McDougall for typing the manuscript.
REFERENCES BECKER, G . & CHEBIB, F. (1969) Simplified computational programming for mixed analysis of variancc designs with equal and unequal subclass numbers. Psychological Reports. 25, 767 -772. BRUNI, J.F.. VAN VUGT, D., MARSHALL, S. & MEITES, J. (1977) Effects of naloxone, morphine and methionine enkephalin on serum prolactin, luteinizing hormone, follicle stimulating hormone, thyrod stimulating hormone and growth hormone. Lfe Srienres. 21,461-466. GOLD, M.S., REDMOND, D.E., Jr. & DONABEDIAN, R.K. (1978) Prolactin secretion, a measurable central effect of opiate-receptor antagonists. Lancet, i. 323- 324. GOLDSTEIN, A. (1976) Opioid peptides (endorphins) in pituitary and brain. Science, 193, 108 I--lOX6. GOMEZ, F., REYES, F.1. & FAIMAN, C. (1977) Nonpuerperal galactorrhea and hyperprolactinemia American Journal of Medicine. 62,648-660. HWANG, P., GUYDA, H. & FRIESEN. H . G . (1971) A radioimniunoassay for human prolactin I’roccwlrnxs National Academy of Sciences, U.S.A..68, 1902-1906. MARTIN, W.R. (1967) Opioid-antagonists. Pharmacological Reviews. 19,463-521. MORGAN, C.R. (1966) Human growth hormone immunoassay: two antibody methods using 1-125 tracer Proreedings of Sociely of Experimenial Biology and Medicine. 121,6244. PERT, C.B. & SNYDER, S.H. (1973) Opiate receptor: demonstration in nervous tissue. S c i t w c , 179, 1011 1014. RIVIER, C., VALE, W., LING, N., BROWN, M. & GUILLEMIN, R. (1977) Stimulation in I ~ I W of the secretion of prolactin and growth hormone by p-endorphin. Endocrinology, 100, 23%241. STlJBBS. W.A., DELITALIA, G . , JONES. A,, JEFFCOATE. W.J., EDWARDS, C R.W., RATTER, S J . ,
Naloxone in acromegaly and hyperprolactinaemia
419
BESSER, G.M., BLOOM, S.R. & ALBERTI, K.G.M.M. (1978) Hormonal and metabolic responses to an enkephalin analogue in normal men. h n c e t . ii, 1225-1227. TOLIS, G., HICKEY, J. & GUYDA, H. (1975) Effects of morphine on serum growth hormone, cortisol, prolactin and thyroid stimulating hormone in man. Journalof Clinical Endocrinology and Metabolism. 41, 797-800. VEZINA, J.L. & SUTTON, T.J. (1974) Prolactin-secreting pituitary microadenomas: roentgenologic diagnosis. American Journal of Roentgenology. Radiotherapy & Nuclear Medicine, 1 2 0 , 4 6 5 4 . VON GRAFFENRIED, B., DEL POZO, E., ROUBICEK, J., KREBS, E., POLDINGER, W., BURMEISTER. P. & KERP, L. (1978) Effects of the synthetic enkephalin analogue FK 33-824 in man. Nature. 272, 729-730.
FAILURE O F NALOXONE T O ALTER GROWTH H O R M O N E AND PROLACTIN LEVELS IN ACROMEGALIC A N D I N HYPERPROLACTINAEMIC PATIENTS J . BLANKSTEIN,* F. REYES, J . WINTER
AND
C . FAIMAN
Departments of Obstetrics and Gynaecology. Physiology, Paediatrics and Medicine, University of Manitoba and the Endocrine- Metabolism Laboratory , Health Sciences Centre, Winnipeg, Manitoba, Canada, R3E 0 2 3 (Received 26 February 1979; reui.red 10 May 1979; accepted 10 May 1979)
SUMMARY
We examined the effects of high-dose intravenous naloxone administration in four acromegalic patients (mean serum growth hormone level 72 ng/ml) and in seven hyperprolactinaemic women (mean serum prolactin level 59 ng/ml), in order to assess whether this opiate antagonist would be effective in lowering growth hormone and prolactin levels. No effect was observed. This lack of effect suggests that an opioid pathway is not involved in the maintenance of elevated growth hormone or prolactin secretion in these patients. However, conclusions regarding the possible role of endogenous opioids in regulation of pituitary function in normal individuals cannot be drawn from this study. The discoveries of opiate receptors in the human central nervous system (Pert & Snyder, 1973) and of endorphins, a group of endogenous substances with opiate-like activity (Goldstein, 1976), have suggested that the latter may function as neurotransmitters capable of influencing those pituitary functions which are known to be affected by exogenous opiates. Thus, it has been shown that administration of morphine results in significant increases of serum growth hormone and prolactin in rats (Rivier et al., 1977; Bruni et al., 1977) and of prolactin in primates, including man (Gold et al., 1978; Tolis et al., 1975). Two recent reports have described a stimulatory effect of an enkephalin analogue upon prolactin and growth hormone secretion in healthy men (Stubbs et al., 1978; von Graffenried el al., 1978). In one of these studies (Stubbs er al., 1978), prior administration of a pure antagonist of opiate action, naloxone, in a dose of 0.4 mg, attenuated the response of both prolactin and growth hormone. The aim of the present study was to assess whether high doses of naloxone would be effective in lowering growth hormone and prolactin levels in acromegalic and hyperprolactinaemic patients. Present address: Department of Obstetrics and Gynaecology, Tel Hashomer Hospital, Israel. Correspondence: Dr. Charles Faiman, (3449-Health Sciences Centre, Department of Endocrinology and Metabolism, 700 William Avenue, Winnipeg, Manitoba, Canada R3E 023.
0300-0664/79/1100-0475W2.00
0 1979 Blackwell Scientific Publications 475
416
J . Blanksteiri et al. PATIENTS A N D METHODS
Four acromegalic patients ranging in age from 34-64 years, and seven hyperprolact inaemic women ranging in age from 20-36 volunteered for this study. The mean serum growth hormone level in the acromegalic group was 72 ng/ml (range 9-220 ng/ml) and the mean serum prolactin level in the hyperprolactinaemic group was 59 ng/ml (range 22-95 ngiml). Pituitary tumours were documented by hypocycloidal sellar tomography (Vezina & Sutton, 1974) in all of the acromegalic and in one of the hyperprolactinaemic patients; the remaining hyperprolactinaemic women did not show signsof a pituitary tumour and were considered dysfunctional (Gomez et al., 1977). The patients reported to the laboratory at 08.00 h and rested for 1 hour. Then a slow intravenous infusion was started, through which 8 ml samples of blood were withdrawn every 15 min over 1 hour. At the beginning of the second hour, naloxone (Endo Laboratories, Garden City, New York supplied in 1 mg/ml and 10 mg/ml ampoules in saline) was infused. The hyperprolactinaemic group received the naloxone by means of a Harvard pump, which delivered 2.3 mg in the first I 5 min, and then 4.5, 1 1 and 23 mg i n each subsequent I5 min period. The total amount infused was 40.8 mg. The acromegalic patients received a bolus of 10 mg in one ml at the beginning of the second hour. During the second hour, blood samples were taken every 5 min in the hyperprolactinaemic group and every 15 min in the acromegalic group. In the third hour blood samples were taken every 15 min. Blood pressure and pulse rate were measured every 10 min throughout the experiment. In four of the hyperprolactinaemic patients and in all acromegalic patients a separate control study was also performed 3 4 weeks later using the same protocol with infusion of identical volumes of saline vehicle only. Measurements of serum prolactin and growth hormone were performed by previously described radioimmunoassay techniques (Hwang el al., 1971; Morgan, 1966). The significance of differences in hormone concentrations between the naloxone- and saline-infused groups, and of pre- versus post-treatment mean levels was assessed by analysis of variance using a mixed factorial design programme (Becker & Chebib, 1969).
RESULTS Prolactin Mean prolactin levels in response to naloxone (40.8 mg) and saline vehicle are shown in Fig. 1. In both groups there was a significant decrease in mean prolactin levels during and after the infusion. However, there was no significant difference between the two groups. Growth Hormone The response to naloxone (10 mg) and saline bolus in four acromegalic patients are shown in Fig. 2. In three patients there were n o significant changes in growth hormone levels following naloxone or saline vehicle administration. In one patient (LN), there was a decline in growth hormone concentrations following naloxone, but a similar response was also obtained following saline injection. Overall, there was no significant difference between pre- and post-naloxone growth hormone levels and between the naloxone and the control growth hormone response. Blood pressure and pulse rate did not change significantly in any of the individuals
Naloxone in acromegaly and hyperprolactinaernia
477
Infusion
-
8- -.--a
E
'\
,.\ \.' '. ,.-.
FT
8-J2\.1..8,,y, ,a Ra. 0'
._ 60 -+=8". 0 L
y
/ \ . , * a
; a
5 50-
- 60
soline(,,=4)
\
\
\
@\
'
8'
J-.&-
I-
*-'.
50
\./*\./Noloxone
a L l ln
(n-7) I
I
I
I
I
I
40
I
260
0
I W
40 -
20 -
5-
I
I
-30 0
I
I
60
I
I
I
I
I
120
I
-30 0
1
I
60
1
I
I
l
120
Time (min)
Fig. 2. Effect of naloxone (solid line) and saline (broken line) o n growth hormone levels in four acromegalic patients. Naloxone (10 mg) or saline vehicle were administered at time 0 (arrows).
following drug or vehicle administration. No psychological or neurological effects were observed throughout the experiment.
DISCUSSION Growth hormone and prolactin levels have been found to increase significantly following administration of morphine and met-enkephalin in the rat; naloxone, an opiate antagonist with virtually n o agonist properties (Martin, 1967), lowered serum growth hormone and prolactin levels (Rivier et al., 1977; Bruni et al., 1977), an observation which suggested that in this species endorphins may participate in the regulation of secretion of these hormones. Morphine also increases serum prolactin levels in monkeys (Gold et al.,
478
J . Blankstein
el
al.
1978) and in man (Tolis et al., 1975). Moreover, synthetic enkephalin analogues were found to have a stimulatory effect on the secretion of growth hormone and prolactin in man (Stubbs et al., 1978; von Graffenried et a/., 1978). Thus one might have expected a naloxone-induced decline in growth hormone and prolactin levels if endogenous opioids were involved in the maintenance of elevated serum levels in pathological conditions. The failure to observe such an effect in acromegalic and hyperprolactinaemic patients would suggest that an opioid pathway is not involved, provided that the amount of naloxone administered (10-40 mg) was sufficient to saturate opioid receptors. This dose of naloxone is 25-100 times higher than the usual adult dose of 0.4 mg used in treating narcotic overdoses, which makes the possibility of failure to fully occupy potential endorphin receptors seem very remote. It is possible that in the acromegalic group and in at least one of the hyperprolactinaemic patients, the lack of response is due to the presence of an autonomously functioning pituitary neoplasm. However, n o neoplasms were detected in six of the latter group, and in these the hyperprolactinaemia is felt to be dysfunctional (Gomez el a / . , 1977). It should be emphasized that the failure of this therapeutic trial in these pathological conditions does not preclude the possibility that endogenous opioids play a role in the physiological regulation of growth hormone and prolactin secretion in man. ACKNOWLEDGEMENTS
Supported in part by the Medical Research Council of Canada (Grant PG-5). The authors wish to thank Dr N. Gupta, Endo Pharmaceuticals, for the kind gift of naloxone. Dr H . G. Friesen, University of Manitoba, for providing the prolactin assay reagents, Dr F. S. Chebib, for helpful statistical advise, M r R. Graham, Ms J . Schilling and Mrs M . Auringer, R. N., for technical assistanceand Ms L. lnsull and Ms J . McDougall for typing the manuscript.
REFERENCES BECKER, G . & CHEBIB, F. (1969) Simplified computational programming for mixed analysis of variancc designs with equal and unequal subclass numbers. Psychological Reports. 25, 767 -772. BRUNI, J.F.. VAN VUGT, D., MARSHALL, S. & MEITES, J. (1977) Effects of naloxone, morphine and methionine enkephalin on serum prolactin, luteinizing hormone, follicle stimulating hormone, thyrod stimulating hormone and growth hormone. Lfe Srienres. 21,461-466. GOLD, M.S., REDMOND, D.E., Jr. & DONABEDIAN, R.K. (1978) Prolactin secretion, a measurable central effect of opiate-receptor antagonists. Lancet, i. 323- 324. GOLDSTEIN, A. (1976) Opioid peptides (endorphins) in pituitary and brain. Science, 193, 108 I--lOX6. GOMEZ, F., REYES, F.1. & FAIMAN, C. (1977) Nonpuerperal galactorrhea and hyperprolactinemia American Journal of Medicine. 62,648-660. HWANG, P., GUYDA, H. & FRIESEN. H . G . (1971) A radioimniunoassay for human prolactin I’roccwlrnxs National Academy of Sciences, U.S.A..68, 1902-1906. MARTIN, W.R. (1967) Opioid-antagonists. Pharmacological Reviews. 19,463-521. MORGAN, C.R. (1966) Human growth hormone immunoassay: two antibody methods using 1-125 tracer Proreedings of Sociely of Experimenial Biology and Medicine. 121,6244. PERT, C.B. & SNYDER, S.H. (1973) Opiate receptor: demonstration in nervous tissue. S c i t w c , 179, 1011 1014. RIVIER, C., VALE, W., LING, N., BROWN, M. & GUILLEMIN, R. (1977) Stimulation in I ~ I W of the secretion of prolactin and growth hormone by p-endorphin. Endocrinology, 100, 23%241. STlJBBS. W.A., DELITALIA, G . , JONES. A,, JEFFCOATE. W.J., EDWARDS, C R.W., RATTER, S J . ,
Naloxone in acromegaly and hyperprolactinaemia
419
BESSER, G.M., BLOOM, S.R. & ALBERTI, K.G.M.M. (1978) Hormonal and metabolic responses to an enkephalin analogue in normal men. h n c e t . ii, 1225-1227. TOLIS, G., HICKEY, J. & GUYDA, H. (1975) Effects of morphine on serum growth hormone, cortisol, prolactin and thyroid stimulating hormone in man. Journalof Clinical Endocrinology and Metabolism. 41, 797-800. VEZINA, J.L. & SUTTON, T.J. (1974) Prolactin-secreting pituitary microadenomas: roentgenologic diagnosis. American Journal of Roentgenology. Radiotherapy & Nuclear Medicine, 1 2 0 , 4 6 5 4 . VON GRAFFENRIED, B., DEL POZO, E., ROUBICEK, J., KREBS, E., POLDINGER, W., BURMEISTER. P. & KERP, L. (1978) Effects of the synthetic enkephalin analogue FK 33-824 in man. Nature. 272, 729-730.
