B.ORMONAL CONTRACEPTIVES AND PLASMA SEX HORMONE BINDING GLOBULIN
M.H. Briggs
Gordon Institute Geelong Australia, 3220
ABSTRACT The concentration of sex hormone binding globulin (SHBG) has been measured in groups of healthy women. There is a 2 ~ o 3-fold increase in women taking combined-type oral contraceptives. Similar increases were seen in volunteers treated with ethynyl-estradiol at various doses for one cycle. In contrast, norgestrel and lynestrenol given alone had no significant effect. Norgestrel partially reversed the estrogen induced increase in SRBG concentration, but lynestrenol did not. The effects of 0.25 mg/d d-norgestrel and 0.50 mg/d dZ-norgestrel on the ethynylestradiol induced change were not significantly different.
Accepted for publication
AUGUST 1975
J une 5, 1975
VOL. 12 NO. 2
149
CONTRACEPTION INTRODUCTION H,-,-- blood plasma contains a 8-globulln of M.W. about i00,000, which shows high binding affinity for both estradiol-17B and testosterone. This plasma protein will be referred to as the sex hormone binding globulin, hereafter abbreviated SHBG. Current knowledge of SHBG has been recently reviewed by Heyns (i), who concludes that there are no marked changes in its plasma concentration during a normal menstrual cycle, though there is a 4-to 8-fold increase during pregnancy. Administration of synthetic estrogens induces a marked increase in SHBG, whereas progestogens, given alone, either have no significant effect, or induce a small decrease. A recent study by van g,mmen et al. (2) has compared various combinations of synthetic estrogens and progestogens, used in oral contraceptives, for their effects on plasma SHBG. The present investigation reports the results of a similar study, but using a different assay method for this protein. A preliminary report has appeared elsewhere (3).
MATERIALS AND
METHODS
Blood was collected from fasting women by venepuncture and plasma separated. Concentration of SKBG was measured using tritiated-5sdihydro-testosterone (Radiochemlcal Centre, Amersham, U.K.) by the method of Anderson et al. (4). All women were healthy volunteers aged 18 to 31 years. Some had received combined-type oral contraceptives for 3 to 8 cycles, while others were just about to start such treatment. Some groups of volunteers received daily doses of ethynylestradlol for 21 consecutive days, then a second cycle of treatment of ethynyl-estradiol plus either d__-norgestrel or lynestrenol. Others received one cycle of treatment wlth only a progestogen. Blood specimens for SHBG measurements were collected at the end of each treatment period. Group mean values and standard deviations were calculated and the statistical significance of differences was evaluated by the calculation of P values by the Student t-test.
RESULTS A s,,mm.ry of findings for each group investigated is set out in Table i.
150
AUGUST 1975
VOL. 12 NO. 2
CONTRACEPTION
Table 1 Plasma SHBG concentrations
Group
Controls
No.
(no treatment)
Ethynylestradlol(EE)
Mean SHBG value (± S.D.) % controls
28
i00" ± 18
alone (cycles)
30 ~g EE/d
12
212
± 31
50 Bg EE/d
15
215
± 36
75 ~g EE/d
i0
285
± 42
50 ~g EE + 0.25 mg d-N
15
189
± 23
50 ~g EE + 0.50 mg dl-N
i0
185
± 28
15
214
± 33
8
95
± 21
0.50 mg dl-N
6
98
± 27
1.00 mg LYN
9
89
± 26
Ethynylestradiol
+ progestogen(cycles)
50 ~g EE + 1.00 mg LYN Progestogen alone (cycle i) 0.25 m g d - N
Oral contraceptives
(cycle 3-8)
(a)
50 ~g EE + 0.50 mg dlN**
12
188
± 28
(b)
50 ~g EE + 0.25 mg d-N***
15
179
± 20
(c)
50 ~g EE + 1.00 mg LYN****
i0
225
± 31
12
182
± 25
(d)
30 Bg EE + 0.15 mg d-N
absolute value (concentration of binding site) = 55 nmol/l
dl-N = d/-norgestrel d-N
= d-norgestrel
LYN
= lynestrenol
AUGUST 1975
VOL. 12 NO. 2
151
CONTRACEPTION
DISCUSSION The results show that the concentration of SRBG in human plasma rises markedly during treatment with ethynylestradiol, alone or in combination with a progestogen. The two progestogens studied (norgestrel and lynestrenol) had no significant effect on SHBG when given alone, though group mean values were somewhat lower than for untreated controls. There was no significant difference in SHBG concentrations in the groups receiving 30 ~g/d or 50 ~g/d ethynylestradiol, but those treated with 75 ~g/d had a significantly higher mean value (P < 0.02). These findings are generally in accord with those of van Kalanen et al. (2). Major differences between the present results and those of this group concern the effect of progestogens on the estrogeninduced change in SHBG, and in the comparative effects of d- and dl-norgestrel. The present findings suggest that norgestrel, but not lynestrenol, antagonises the estrogen effect and reduces the stimulatory action of ethynylestradiol on SHBG concentration. A similar finding is reported elsewhere for several other plasma proteins (3). In none of the present groups was there any difference in effects on SHBG between 0.25 mg d-norgestrel and 0.50 mg dZ-norgestrel. The difference reported by van Kammen et al.(2) could not be detected and the occurrence of such a difference would be most surprising in view of the lack of hormonal properties in the ~(+)-enantiomorph of norgestrel (5,6).
152
AUGUST 1975
VOL. 12 NO. 2
CONTRACEPTION
REFERENCES 1.
Heyns, W.: The steroid-blnding B-globulin of h, mmn plasma. Adv. Steroid Biochem. Pharmacol. 6: in press (1975)
2.
van K ~ n , E . , T h i J s s e n , J . H . H . , Rademaker, B. and Schwarz, F. The influence of hormonal contraceptives on sex hormone b i n d i n g globulin (SKBG) capacity. Contraception ii: 53-59 (1975)
3.
Brlggs, M.H. Effects of oral progestogens on estrogen-induced changes in serum proteins. Excerpta Medica Int. Congr. Set. 344:35-41 (1974)
4.
Anderson, D.C., Peppiatt, R., Schuster, L. and Fisher, R. A new method for measurement of sex-hormone binding globulin in plasma and its clinical application. J. Endoer. 55: xi-xli(1972)
5.
Edgren, R.A., Smith, H., Hughes, G.A., Smith, L.L. and Gree~span, G. Biological effects of racemic and resolved l~-B-ethyl-4-gonen3-ones. Steroids 2:731-737 (1963)
6.
Briggs, M.H. Contraceptive steroid binding to the human uterine progesterone receptor. Cur. Med. Res. Opln. 3:95-98 (1975).
A U G U S T 1975
VOL. 12 NO. 2
153
M.H. Briggs
Gordon Institute Geelong Australia, 3220
ABSTRACT The concentration of sex hormone binding globulin (SHBG) has been measured in groups of healthy women. There is a 2 ~ o 3-fold increase in women taking combined-type oral contraceptives. Similar increases were seen in volunteers treated with ethynyl-estradiol at various doses for one cycle. In contrast, norgestrel and lynestrenol given alone had no significant effect. Norgestrel partially reversed the estrogen induced increase in SRBG concentration, but lynestrenol did not. The effects of 0.25 mg/d d-norgestrel and 0.50 mg/d dZ-norgestrel on the ethynylestradiol induced change were not significantly different.
Accepted for publication
AUGUST 1975
J une 5, 1975
VOL. 12 NO. 2
149
CONTRACEPTION INTRODUCTION H,-,-- blood plasma contains a 8-globulln of M.W. about i00,000, which shows high binding affinity for both estradiol-17B and testosterone. This plasma protein will be referred to as the sex hormone binding globulin, hereafter abbreviated SHBG. Current knowledge of SHBG has been recently reviewed by Heyns (i), who concludes that there are no marked changes in its plasma concentration during a normal menstrual cycle, though there is a 4-to 8-fold increase during pregnancy. Administration of synthetic estrogens induces a marked increase in SHBG, whereas progestogens, given alone, either have no significant effect, or induce a small decrease. A recent study by van g,mmen et al. (2) has compared various combinations of synthetic estrogens and progestogens, used in oral contraceptives, for their effects on plasma SHBG. The present investigation reports the results of a similar study, but using a different assay method for this protein. A preliminary report has appeared elsewhere (3).
MATERIALS AND
METHODS
Blood was collected from fasting women by venepuncture and plasma separated. Concentration of SKBG was measured using tritiated-5sdihydro-testosterone (Radiochemlcal Centre, Amersham, U.K.) by the method of Anderson et al. (4). All women were healthy volunteers aged 18 to 31 years. Some had received combined-type oral contraceptives for 3 to 8 cycles, while others were just about to start such treatment. Some groups of volunteers received daily doses of ethynylestradlol for 21 consecutive days, then a second cycle of treatment of ethynyl-estradiol plus either d__-norgestrel or lynestrenol. Others received one cycle of treatment wlth only a progestogen. Blood specimens for SHBG measurements were collected at the end of each treatment period. Group mean values and standard deviations were calculated and the statistical significance of differences was evaluated by the calculation of P values by the Student t-test.
RESULTS A s,,mm.ry of findings for each group investigated is set out in Table i.
150
AUGUST 1975
VOL. 12 NO. 2
CONTRACEPTION
Table 1 Plasma SHBG concentrations
Group
Controls
No.
(no treatment)
Ethynylestradlol(EE)
Mean SHBG value (± S.D.) % controls
28
i00" ± 18
alone (cycles)
30 ~g EE/d
12
212
± 31
50 Bg EE/d
15
215
± 36
75 ~g EE/d
i0
285
± 42
50 ~g EE + 0.25 mg d-N
15
189
± 23
50 ~g EE + 0.50 mg dl-N
i0
185
± 28
15
214
± 33
8
95
± 21
0.50 mg dl-N
6
98
± 27
1.00 mg LYN
9
89
± 26
Ethynylestradiol
+ progestogen(cycles)
50 ~g EE + 1.00 mg LYN Progestogen alone (cycle i) 0.25 m g d - N
Oral contraceptives
(cycle 3-8)
(a)
50 ~g EE + 0.50 mg dlN**
12
188
± 28
(b)
50 ~g EE + 0.25 mg d-N***
15
179
± 20
(c)
50 ~g EE + 1.00 mg LYN****
i0
225
± 31
12
182
± 25
(d)
30 Bg EE + 0.15 mg d-N
absolute value (concentration of binding site) = 55 nmol/l
dl-N = d/-norgestrel d-N
= d-norgestrel
LYN
= lynestrenol
AUGUST 1975
VOL. 12 NO. 2
151
CONTRACEPTION
DISCUSSION The results show that the concentration of SRBG in human plasma rises markedly during treatment with ethynylestradiol, alone or in combination with a progestogen. The two progestogens studied (norgestrel and lynestrenol) had no significant effect on SHBG when given alone, though group mean values were somewhat lower than for untreated controls. There was no significant difference in SHBG concentrations in the groups receiving 30 ~g/d or 50 ~g/d ethynylestradiol, but those treated with 75 ~g/d had a significantly higher mean value (P < 0.02). These findings are generally in accord with those of van Kalanen et al. (2). Major differences between the present results and those of this group concern the effect of progestogens on the estrogeninduced change in SHBG, and in the comparative effects of d- and dl-norgestrel. The present findings suggest that norgestrel, but not lynestrenol, antagonises the estrogen effect and reduces the stimulatory action of ethynylestradiol on SHBG concentration. A similar finding is reported elsewhere for several other plasma proteins (3). In none of the present groups was there any difference in effects on SHBG between 0.25 mg d-norgestrel and 0.50 mg dZ-norgestrel. The difference reported by van Kammen et al.(2) could not be detected and the occurrence of such a difference would be most surprising in view of the lack of hormonal properties in the ~(+)-enantiomorph of norgestrel (5,6).
152
AUGUST 1975
VOL. 12 NO. 2
CONTRACEPTION
REFERENCES 1.
Heyns, W.: The steroid-blnding B-globulin of h, mmn plasma. Adv. Steroid Biochem. Pharmacol. 6: in press (1975)
2.
van K ~ n , E . , T h i J s s e n , J . H . H . , Rademaker, B. and Schwarz, F. The influence of hormonal contraceptives on sex hormone b i n d i n g globulin (SKBG) capacity. Contraception ii: 53-59 (1975)
3.
Brlggs, M.H. Effects of oral progestogens on estrogen-induced changes in serum proteins. Excerpta Medica Int. Congr. Set. 344:35-41 (1974)
4.
Anderson, D.C., Peppiatt, R., Schuster, L. and Fisher, R. A new method for measurement of sex-hormone binding globulin in plasma and its clinical application. J. Endoer. 55: xi-xli(1972)
5.
Edgren, R.A., Smith, H., Hughes, G.A., Smith, L.L. and Gree~span, G. Biological effects of racemic and resolved l~-B-ethyl-4-gonen3-ones. Steroids 2:731-737 (1963)
6.
Briggs, M.H. Contraceptive steroid binding to the human uterine progesterone receptor. Cur. Med. Res. Opln. 3:95-98 (1975).
A U G U S T 1975
VOL. 12 NO. 2
153
