HORMONES
AND
BEHAVIOR
Plasma
9, 19-22 (1977)
Prolactin
Levels in Male Homosexuals
RICHARD C.FRIEDMAN AND ANDREWG.FRANTZ Departments of Psychiatry and Medicine, Columbia University, College of Physicians and Surgeons, International Institute of Human Reproduction, 630 West 168th Street, New York, New York 10032
Plasma prolactin values of 20 male homosexuals of Kinsey rating 6 were compared with plasma prolactin values of 15 male heterosexuals of Kinsey rating 0. There was no difference in mean plasma prolactin value between the two groups. These findings are at variance with those reported by Kolodny et al. [Kolodny, R. C., Jacobs, L. S., Masters, W. H., Toro, G., and Daughaday, W. H. (1971a). Plasma gonadotrophins and prolactin in male homosexuals. Lancer 2, 18-201 in which plasma prolactin was found to be elevated in individuals of Kinsey rating 6 as compared to heterosexual controls. The present investigation, therefore, fails to confirm a relationship between sexual orientation in males and plasma prolactin level.
Studies of hormones in males of divergent sexual-object preference have revealed differences in some cases (Kolodny et al., 1971a,b; Margolese, 1970; Margolese and Janiger, 1973; Evans, 1972; Dorner et al., 1971; Doerr et al., 1973; Dorner et al., 1975; Starka et al., 1975; Doerr et al., 1976) and no differences in others (Tourney and Hatfield, 1972; Birk et al., 1973; Brodie et al., 1974; Tourney et al., 1975; Barlow et al., 1974; Friedman et al., in press). Data are still too sparse for a conclusion to be reached about the relationship between hormones and sexual orientation in humans. In 1971(a), Kolodny et al. described serum prolactin differences between males at the polar extremes of the homosexual-heterosexual continuum. This finding was difficult to interpret in view of the small number of subjects in the investigation. It was tentatively suggested, however, that the increased serum prolactin in the group of homosexual subjects of Kinsey rating 6 might reflect hypothalamic dysfunction, possibly failure of inhibition of pituitary prolactin secretion by prolactininhibiting factor (PIF). Attempts have been made to confirm the wellknown findings of Kolodny et al. (1971a) with regard to the hypothalamic-pituitary sex steroid systems (Tourney and Hatfield, 1972; Doerr et al., 1973; Birk et al., 1973; Brodie et al., 1974; Barlow et al., 1974; Tourney et al., 1975; Starka et al., 1975; Doerr et al., 1976). This Copyright All rights
@ 1977 by Academic Press, Inc. of reproduction in any form reserved.
19 ISSN 0018-506X
20
FRIEDMAN
AND
FRANTZ
pilot study is the first in which an attempt was made to confirm the findings of Kolodny et al. (197la) with regard to prolactin. METHODS
All subjects in the study were white males, in good health and on no medication that is known to affect serum prolactin (Frantz, 1973). Homosexual subjects were referred by a homosexual psychiatrist or a homosexual clinical psychologist. Efforts were made to enlist individuals who were known to be lifelong Kinsey 6 homosexuals and who were socially well integrated. The mean age of homosexual subjects was 32 (range 23-42). Heterosexual subjects were referred by a heterosexual medical student and a heterosexual psychiatrist. The mean age of heterosexual subjects was 28 (range 21-40). All participants in the study received financial renumeration. Detailed sexual history was taken by the senior author. Each subject had been in his respective Kinsey group, in fantasy from the onset of erotic fantasy life, and in activity from the onset of sexual activity with others. All subjects were sexually active and had experienced orgasm with a partner during the week prior to sampling. No subject, however, experienced orgasm within 24 hr of bloodletting. Individuals were excluded from the study if there were signs of affective distress at the initial interview or if, in the clinical judgment of the senior author, severe psychopathology was present during the previous week. Two homosexual subjects were excluded: one because of multiple drug abuse and probable opiate addiction and the other because of severe ideas of reference and chronic anxiety. After 10 min of rest in the supine position, 7 ml of venous blood was taken between 9:30 and IO:30 AM. All subjects were calm, without evidence of anxiety at the time of sampling. Prolactin was measured by a homologous human radioimmunoassay; details of the precision, sensitivity, and other characteristics of this assay have previously been described (Frantz, 1976). RESULTS
The results are given in Table 1. No significant difference was found between the serum prolactin levels of the homosexuals as compared with those of the heterosexuals. DISCUSSION
The data of this pilot investigation are admittedly limited. Our subjects were, however, selected with great care. In order to maximize the probability of finding hormonal differences, we studied only two groups of men who were well differentiated with regard to sexual orientation. Our results suggest that there is no necessary relationship between sexual orientation
PROLACTIN
21
IN MALE HOMOSEXUALS
TABLE 1 Serum Prolactin in Homosexual and Heterosexual Males Homosexuals Subject
Heterosexuals
Prolactin
Subject
Prolactin (ndml)
A B C D E F G H I J K L M N 0
4.5 6.5 11.2 11.2 7.4 5.9 5.5 6.2 6.4 11.0 8.0 7.1 5.1 6.4 8.9
(w/ml)
1 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 Mean” + SD n
9.6 6.9 6.2 6.1 I .6 7.4 7.5 6.9 5.4 4.1 9.8 4.5 8.2 10.6 9.3 7.6 7.2 6.8 8.4 6. I 7.01 2.13 20
6.72 2.62 15
a Difference not statistically significant.
and serum prolactin in human males. It is still possible that our homosexual and heterosexual subjects differed with regard to responsitivity of the hypothalamic-pituitary axis to higher controlling mechanisms. Thus, the two groups could theoretically respond differently to alterations of dopaminergic transmission, such as those effected by administration of phenothiazines, for example. Unfortunately, it was not possible for us to clarify this issue in the present investigation. The discrepancy between our findings and those reported by Kolodny et al. (1971a,b) is compatible with the hypothesis that subgroups of exclusively homosexual men exist who differ with regard to endocrine status. In some subgroups, hormonal abnormalities of various types occur. These may be related to sexual orientation as causes, as effects, or as both. In other subgroups endocrine function is normal. Further studies are needed to clarify the relationship between hypothalamic-pituitary functioning and sexual orientation in humans.
22
FRIEDMAN
AND FRANTZ
ACKNOWLEDGMENTS We are grateful to Mrs. Annette Topilow for her help with the administrative aspects of this study. Mr. Robert E. Sundeen and Mrs. Irene Conwell provided expert technical assistance. This work was supported by NIH Grants 5 PO1 HD 06132 and 5 ROI CA II704 and by a grant from the New York Foundation.
REFERENCES Barlow, D., Abel, G., Blanchard, E., and Mavissakalian, M. (1974). Plasma testosterone levels and male homosexuality: A failure to replicate. Arch. Sex. Behav. 3, 571-575. Birk, L., Williams, G., Chasin, M., and Rose, L. (1973). Serum testosterone levels in homosexual men. N. Engl. J. Med. 289, 1236-1238. Brodie, H. K. H., Gartrell, N., Doering, C., and Fhue, T. (1974). Plasma testosterone levels in heterosexual and homosexual men. Amer. J. Psychiat. 131, 82-83. Doerr, P., Kockett, G., Vogt, H. J., Pirke, K. M., and Dittmar, F. (1973). Plasma testosterone, estradiol, and semen analysis in male homosexuals. Arch. Gen. Psychiat. 29, 829-834.
Doerr, P., Pirke, K. M., Kockett, G., and Dittmar, F. (1976). Further studies on sex hormones in male homosexuals. Arch. Gen. Psychiat. 33, 61 I-615. Dorner, V. G., Rohde, W., and Krell, L. (1971). Auslosung eines positiven Ostro60, 297-301. genfeedback-effekt bei homosexuellen Mannern. Endokrinologie Dorner, G., Rohde, W., Stahl, F., Krell, L., and Masius, W. G. (1975). A neuroendocrine predisposition for homosexuality in men. Arch. Sex. Behav. 4, l-9. Evans, R. (1972). Physical and biochemical characteristics of homosexual men. J. Consul?. Clin. Psychiat. 39, 140-147. Frantz, A. G. (1976). Prolactin: Bioassay and radioimmunoassay. In Antoniades, H. N. (Ed.), Hormones in Human Plasma, 2nd ed., pp. 449-463. Little, Brown, Boston. Frantz, A. G. (1973). The regulation of prolactin secretion in humans. In L. Martini and W. F. Ganong (Eds.), Frontiers in Neuroendocrinology 1973, pp. 337-374. Oxford University Press, New York. Friedman, R. C., Wollensen, F., and Tendler, R. (1976). Psychological development and blood levels of sex steroids in male identical twins of divergent sexual orientation. J. Nerv.
Ment. Dis. 163, 282-288.
Kolodny, R. C., Jacobs, L. S., Masters, W. H., Toro, G., and Daughaday, W. H. (1971a). Plasma gonadotrophins and prolactin in male homosexuals. Lancet 2, 18-20. Kolodny, R. C., Masters, W. H., Hendryx, J., and Toro, G. (197lb). Plasma testosterone and semen analysis in male homosexuals. N. Engl. J. Med. 285, 1170-l 174. Margolese, M. S. (1970). Homosexuality: A new endocrine correlate. Horm. Behav. 1, 151-155. Margolese, M. S., and Janiger, 0. (1973). Androsteroneietiocholanolone ration in male homosexuals. Brit. Med. J. 3, 207-210. Starka, L., Sipova, I., and Hynie, J. (1975). Plasma testosterone in male transsexuals and homosexuals. J. Sex. Res. 11, 134-138. Tourney, G., and Hatfield, L. M. (1972). Androgen Metabolism in Schizophrenics, Homosexuals and Nor-mcrl Controls. Presented at the 27th annual meeting of the Society of Biological Psychiatry, Dallas, Texas, April 28-30, 1972. Tourney, B., Petrilli, A. J., and Hatfield, L. M. (1975). Hormonal relationships in homosexual men. Amer. J. Psychiat. 132, 288-290.
AND
BEHAVIOR
Plasma
9, 19-22 (1977)
Prolactin
Levels in Male Homosexuals
RICHARD C.FRIEDMAN AND ANDREWG.FRANTZ Departments of Psychiatry and Medicine, Columbia University, College of Physicians and Surgeons, International Institute of Human Reproduction, 630 West 168th Street, New York, New York 10032
Plasma prolactin values of 20 male homosexuals of Kinsey rating 6 were compared with plasma prolactin values of 15 male heterosexuals of Kinsey rating 0. There was no difference in mean plasma prolactin value between the two groups. These findings are at variance with those reported by Kolodny et al. [Kolodny, R. C., Jacobs, L. S., Masters, W. H., Toro, G., and Daughaday, W. H. (1971a). Plasma gonadotrophins and prolactin in male homosexuals. Lancer 2, 18-201 in which plasma prolactin was found to be elevated in individuals of Kinsey rating 6 as compared to heterosexual controls. The present investigation, therefore, fails to confirm a relationship between sexual orientation in males and plasma prolactin level.
Studies of hormones in males of divergent sexual-object preference have revealed differences in some cases (Kolodny et al., 1971a,b; Margolese, 1970; Margolese and Janiger, 1973; Evans, 1972; Dorner et al., 1971; Doerr et al., 1973; Dorner et al., 1975; Starka et al., 1975; Doerr et al., 1976) and no differences in others (Tourney and Hatfield, 1972; Birk et al., 1973; Brodie et al., 1974; Tourney et al., 1975; Barlow et al., 1974; Friedman et al., in press). Data are still too sparse for a conclusion to be reached about the relationship between hormones and sexual orientation in humans. In 1971(a), Kolodny et al. described serum prolactin differences between males at the polar extremes of the homosexual-heterosexual continuum. This finding was difficult to interpret in view of the small number of subjects in the investigation. It was tentatively suggested, however, that the increased serum prolactin in the group of homosexual subjects of Kinsey rating 6 might reflect hypothalamic dysfunction, possibly failure of inhibition of pituitary prolactin secretion by prolactininhibiting factor (PIF). Attempts have been made to confirm the wellknown findings of Kolodny et al. (1971a) with regard to the hypothalamic-pituitary sex steroid systems (Tourney and Hatfield, 1972; Doerr et al., 1973; Birk et al., 1973; Brodie et al., 1974; Barlow et al., 1974; Tourney et al., 1975; Starka et al., 1975; Doerr et al., 1976). This Copyright All rights
@ 1977 by Academic Press, Inc. of reproduction in any form reserved.
19 ISSN 0018-506X
20
FRIEDMAN
AND
FRANTZ
pilot study is the first in which an attempt was made to confirm the findings of Kolodny et al. (197la) with regard to prolactin. METHODS
All subjects in the study were white males, in good health and on no medication that is known to affect serum prolactin (Frantz, 1973). Homosexual subjects were referred by a homosexual psychiatrist or a homosexual clinical psychologist. Efforts were made to enlist individuals who were known to be lifelong Kinsey 6 homosexuals and who were socially well integrated. The mean age of homosexual subjects was 32 (range 23-42). Heterosexual subjects were referred by a heterosexual medical student and a heterosexual psychiatrist. The mean age of heterosexual subjects was 28 (range 21-40). All participants in the study received financial renumeration. Detailed sexual history was taken by the senior author. Each subject had been in his respective Kinsey group, in fantasy from the onset of erotic fantasy life, and in activity from the onset of sexual activity with others. All subjects were sexually active and had experienced orgasm with a partner during the week prior to sampling. No subject, however, experienced orgasm within 24 hr of bloodletting. Individuals were excluded from the study if there were signs of affective distress at the initial interview or if, in the clinical judgment of the senior author, severe psychopathology was present during the previous week. Two homosexual subjects were excluded: one because of multiple drug abuse and probable opiate addiction and the other because of severe ideas of reference and chronic anxiety. After 10 min of rest in the supine position, 7 ml of venous blood was taken between 9:30 and IO:30 AM. All subjects were calm, without evidence of anxiety at the time of sampling. Prolactin was measured by a homologous human radioimmunoassay; details of the precision, sensitivity, and other characteristics of this assay have previously been described (Frantz, 1976). RESULTS
The results are given in Table 1. No significant difference was found between the serum prolactin levels of the homosexuals as compared with those of the heterosexuals. DISCUSSION
The data of this pilot investigation are admittedly limited. Our subjects were, however, selected with great care. In order to maximize the probability of finding hormonal differences, we studied only two groups of men who were well differentiated with regard to sexual orientation. Our results suggest that there is no necessary relationship between sexual orientation
PROLACTIN
21
IN MALE HOMOSEXUALS
TABLE 1 Serum Prolactin in Homosexual and Heterosexual Males Homosexuals Subject
Heterosexuals
Prolactin
Subject
Prolactin (ndml)
A B C D E F G H I J K L M N 0
4.5 6.5 11.2 11.2 7.4 5.9 5.5 6.2 6.4 11.0 8.0 7.1 5.1 6.4 8.9
(w/ml)
1 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 Mean” + SD n
9.6 6.9 6.2 6.1 I .6 7.4 7.5 6.9 5.4 4.1 9.8 4.5 8.2 10.6 9.3 7.6 7.2 6.8 8.4 6. I 7.01 2.13 20
6.72 2.62 15
a Difference not statistically significant.
and serum prolactin in human males. It is still possible that our homosexual and heterosexual subjects differed with regard to responsitivity of the hypothalamic-pituitary axis to higher controlling mechanisms. Thus, the two groups could theoretically respond differently to alterations of dopaminergic transmission, such as those effected by administration of phenothiazines, for example. Unfortunately, it was not possible for us to clarify this issue in the present investigation. The discrepancy between our findings and those reported by Kolodny et al. (1971a,b) is compatible with the hypothesis that subgroups of exclusively homosexual men exist who differ with regard to endocrine status. In some subgroups, hormonal abnormalities of various types occur. These may be related to sexual orientation as causes, as effects, or as both. In other subgroups endocrine function is normal. Further studies are needed to clarify the relationship between hypothalamic-pituitary functioning and sexual orientation in humans.
22
FRIEDMAN
AND FRANTZ
ACKNOWLEDGMENTS We are grateful to Mrs. Annette Topilow for her help with the administrative aspects of this study. Mr. Robert E. Sundeen and Mrs. Irene Conwell provided expert technical assistance. This work was supported by NIH Grants 5 PO1 HD 06132 and 5 ROI CA II704 and by a grant from the New York Foundation.
REFERENCES Barlow, D., Abel, G., Blanchard, E., and Mavissakalian, M. (1974). Plasma testosterone levels and male homosexuality: A failure to replicate. Arch. Sex. Behav. 3, 571-575. Birk, L., Williams, G., Chasin, M., and Rose, L. (1973). Serum testosterone levels in homosexual men. N. Engl. J. Med. 289, 1236-1238. Brodie, H. K. H., Gartrell, N., Doering, C., and Fhue, T. (1974). Plasma testosterone levels in heterosexual and homosexual men. Amer. J. Psychiat. 131, 82-83. Doerr, P., Kockett, G., Vogt, H. J., Pirke, K. M., and Dittmar, F. (1973). Plasma testosterone, estradiol, and semen analysis in male homosexuals. Arch. Gen. Psychiat. 29, 829-834.
Doerr, P., Pirke, K. M., Kockett, G., and Dittmar, F. (1976). Further studies on sex hormones in male homosexuals. Arch. Gen. Psychiat. 33, 61 I-615. Dorner, V. G., Rohde, W., and Krell, L. (1971). Auslosung eines positiven Ostro60, 297-301. genfeedback-effekt bei homosexuellen Mannern. Endokrinologie Dorner, G., Rohde, W., Stahl, F., Krell, L., and Masius, W. G. (1975). A neuroendocrine predisposition for homosexuality in men. Arch. Sex. Behav. 4, l-9. Evans, R. (1972). Physical and biochemical characteristics of homosexual men. J. Consul?. Clin. Psychiat. 39, 140-147. Frantz, A. G. (1976). Prolactin: Bioassay and radioimmunoassay. In Antoniades, H. N. (Ed.), Hormones in Human Plasma, 2nd ed., pp. 449-463. Little, Brown, Boston. Frantz, A. G. (1973). The regulation of prolactin secretion in humans. In L. Martini and W. F. Ganong (Eds.), Frontiers in Neuroendocrinology 1973, pp. 337-374. Oxford University Press, New York. Friedman, R. C., Wollensen, F., and Tendler, R. (1976). Psychological development and blood levels of sex steroids in male identical twins of divergent sexual orientation. J. Nerv.
Ment. Dis. 163, 282-288.
Kolodny, R. C., Jacobs, L. S., Masters, W. H., Toro, G., and Daughaday, W. H. (1971a). Plasma gonadotrophins and prolactin in male homosexuals. Lancet 2, 18-20. Kolodny, R. C., Masters, W. H., Hendryx, J., and Toro, G. (197lb). Plasma testosterone and semen analysis in male homosexuals. N. Engl. J. Med. 285, 1170-l 174. Margolese, M. S. (1970). Homosexuality: A new endocrine correlate. Horm. Behav. 1, 151-155. Margolese, M. S., and Janiger, 0. (1973). Androsteroneietiocholanolone ration in male homosexuals. Brit. Med. J. 3, 207-210. Starka, L., Sipova, I., and Hynie, J. (1975). Plasma testosterone in male transsexuals and homosexuals. J. Sex. Res. 11, 134-138. Tourney, G., and Hatfield, L. M. (1972). Androgen Metabolism in Schizophrenics, Homosexuals and Nor-mcrl Controls. Presented at the 27th annual meeting of the Society of Biological Psychiatry, Dallas, Texas, April 28-30, 1972. Tourney, B., Petrilli, A. J., and Hatfield, L. M. (1975). Hormonal relationships in homosexual men. Amer. J. Psychiat. 132, 288-290.
