A method for measurement of free testosterone in premenopausal women involving equilibrium dialysis, chromatography, and radioimmunoassay

A three-step procedure to evaluate the quantity of true free testosterone in female serum was established. Unbound and bound testosterone were first separated by equilibrium dialysis using undiluted serum. Testosterone in dialysate was extracted and separated from cross-reactive steroids by column chromatography and finally quantified with a sensitive radioimmunoassay. The detection limit of the radioimmunoassay was 2.7 pmol/L and the detection limit of the whole method was 6 pmol/L. The intra-assay coefficients of variation of the method were 20.6%, 16.8%, and 9.5% for free testosterone concentrations 12.0 pmol/L, 21.4 pmol/L, and 31.4 pmol/L, respectively. The interassay coefficients of variation were 26.3% and 14.8% for free testosterone concentrations 10.4 pmol/L and 21.3 pmol/L, respectively. Serum free testosterone concentrations were determined in 27 regularly menstruating control women. The mean concentration of actual free testosterone was 10.0 +/- 4.9 pmol/L (mean +/- SD, range from below 6 to 19 pmol/L, n = 27).

Steroid hormone receptors and flow cytometric DNA ploidy in ovarian carcinoma

The biochemical and immunohistochemical estrogen (ER) and progesterone receptor (PR) content and flow cytometric DNA ploidy was analyzed in five semimalignant and 35 malignant epithelial ovarian tumours. By biochemical assay, 67% of the tumours were ER-positive (> or = 5 fmol/mg protein) and 56% were PR-positive (> or = 10 fmol/mg protein). The corresponding values by immunohistochemical assay (with a HSCORE of 10 as the cutoff level) were 22% and 27%, respectively. DNA histogram measured from paraffin embedded specimens were diploid in 20% (7/35) and aneuploid in 80% (28/35) of the malignant tumours. All semimalignant tumours were diploid. The mean receptor values in the diploid and aneuploid tumours did not differ significantly and receptor-positive and receptor-negative tumours were evenly distributed in all stages and grades. In contrast, flow cytometric DNA ploidy was clearly associated with tumour stage (G2 = 10.52, Df = 3, P = 0.015) and histological differentiation (G2 = 20.57, Df = 3, P = 0.0001).

Serum androgen and gonadotropin levels decline after progestogen-induced withdrawal bleeding in oligomenorrheic women with or without polycystic ovaries

OBJECTIVE

To examine the effect of short-term progestogen treatment on androgen, gonadotropin, and sex hormone-binding globulin (SHBG) levels in oligomenorrheic women.

DESIGN

Comparative study of changes in hormonal parameters in patients with or without ultrasonographically diagnosed polycystic ovarian disease (PCOD).

SETTING

Open patient clinic of reproductive endocrinology at University Central Hospital of Turku, Finland.

PATIENTS

Seventy-five oligomenorrheic women with (n = 51) or without (n = 24) PCOD.

MAIN OUTCOME MEASURES

Serum concentrations of testosterone (T), androstenedione (A), dehydroepiandrosterone sulfate, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and SHBG.

RESULTS

The levels of T, A, LH, and the LH:FSH ratios decreased significantly after oral treatment with medroxyprogesterone acetate (10 mg/d for 10 days) in non-PCOD women and in women with PCOD decreasing the frequencies of pathological laboratory findings, in particular elevated levels of LH:FSH ratio and A in PCOD women and of LH:FSH ratio in non-PCOD women. The levels of T, A, and LH as well as the LH:FSH ratio were significantly higher in women with PCOD. Obesity was associated with high free androgen indices, low LH:FSH ratios, and low concentrations of LH, A, and SHBG.

CONCLUSIONS

The serum samples for hormonal analyses used as an aid in diagnosing PCOD should be obtained without pretreatment with progestogen because it masks the biochemical findings of PCOD.

Reference intervals for serum sex steroids and gonadotropins in regularly menstruating women

Reference intervals for novel fluoro-immunoassays for serum luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P) were established in 40 healthy regularly menstruating women. Serum samples for sex steroids, including testosterone (T), androstenedione (A) and dehydroepiandrosterone sulphate (DHEAS), as well as sex hormone binding globulin (SHBG) and gonadotropins, were collected in the early follicular and mid-luteal phases of the menstrual cycle. The need for the timing of androgen and gonadotropin samples was also determinated. Serum E2 and P were measured by radio-immuno- and time-resolved fluoro-immunoassays. Various assay methods correlated closely, but the reference intervals varied considerably from one method to another. In the early follicular phase the LH/FSH ratio only ranged between 0.2 and 1.7 (mean +/- S.D.; 0.8 +/- 0.3); the variation was greater (from 0.3 to 3.5) in the luteal phase, when the mean was also significantly higher (1.5 +/- 0.9, p = 0.0001). Similarly the mean values of T and SHBG were higher in the luteal phase, while the other androgen concentrations and calculated androgen indexes were equal, compared with the follicular phase values. Thus the timing of hormone determinations is warranted in the investigation of the gonadotropin and androgen status in normally menstruating women. Moreover, the upper limit of the LH/FSH ratio examined with new, sensitive methods is lower than that previously stated. The use of an intra-uterine contraceptive device (IUD) had no effect on hormone levels.

Two new two-step immunoassays for free thyroxin evaluated: solid-phase radioimmunoassay and time-resolved fluoroimmunoassay

We measured concentrations of free thyroxin (FT4) in serum by using two new two-step FT4 assays--a solid-phase two-step radioimmunoassay. Spectria, and a time-resolved fluoroimmunoassay. Delfia--and compared the results with those by a two-step FT4 assay (RIA-gnost), a one-step FT4 analog assay (Amerlex-M), and FT4 measured after equilibrium dialysis. The new FT4 assays classified 30 hypothyroid and 43 hyperthyroid patients (untreated) well. In 138 patients with nonthyroidal illness (NTI) and in late pregnancy (n = 36), fewer subnormal FT4 values were reported by Spectria (P less than 0.001), Delfia (P less than 0.001), and RIA-gnost (P less than 0.01) than by Amerlex-M. The results of the Spectria and Delfia methods correlated with the results of the dialysis method (r = 0.76) in NTI patients and pregnancy, and were in better agreement with the clinical state than was FT4 by Amerlex-M. The FT4 values by Amerlex-M, but not by other methods, correlated with albumin concentration. We conclude that these new two-step methods present good alternatives for FT4 analysis.

Two new two-step immunoassays for free thyroxin evaluated: solid-phase radioimmunoassay and time-resolved fluoroimmunoassay

We measured concentrations of free thyroxin (FT4) in serum by using two new two-step FT4 assays--a solid-phase two-step radioimmunoassay. Spectria, and a time-resolved fluoroimmunoassay. Delfia--and compared the results with those by a two-step FT4 assay (RIA-gnost), a one-step FT4 analog assay (Amerlex-M), and FT4 measured after equilibrium dialysis. The new FT4 assays classified 30 hypothyroid and 43 hyperthyroid patients (untreated) well. In 138 patients with nonthyroidal illness (NTI) and in late pregnancy (n = 36), fewer subnormal FT4 values were reported by Spectria (P less than 0.001), Delfia (P less than 0.001), and RIA-gnost (P less than 0.01) than by Amerlex-M. The results of the Spectria and Delfia methods correlated with the results of the dialysis method (r = 0.76) in NTI patients and pregnancy, and were in better agreement with the clinical state than was FT4 by Amerlex-M. The FT4 values by Amerlex-M, but not by other methods, correlated with albumin concentration. We conclude that these new two-step methods present good alternatives for FT4 analysis.

Androgen parameters in hirsute women: correlations with body mass index and age

The recent work was designed for studying the effects of body mass index (BMI) and age on serum hormone values in hirsute women of reproductive years with nontumorous hyperandrogenism. Two hundred patients were studied in the follicular phase of the cycle. The serum levels of testosterone (T), androstenedione (A), or dehydroepiandrosterone sulfate (DHEAS) were not associated with BMI, whereas the T/sex hormone-binding globulin (T/SHBG) ratio was significantly correlated with BMI independently of the effect of age. All serum androgens were significantly negatively correlated with age, and the serum levels were significantly lower in women older than 41 years when compared with women aged 25 years or less. After correcting for the effect of BMI, there was also a negative correlation between the T/SHBG ratio and age. The correlations between serum androgen parameters were calculated. We conclude that already in reproductive years, the age of the patient has modulating effects on serum androgens, and it should be taken into account when studying the hormone profile of hirsute women.

Endocrine status and growth after malignancy treated in childhood or adolescence

Six girls and three boys, asymptomatic after treatment for acute lymphoblastic leukemia (ALL) or endodermal sinus tumor (EST), were investigated for endocrine status and growth. Serum follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), prolactin (PRL), testosterone (T), androstenedione (A), dehydroepiandrosterone sulfate (DHEAS), testosterone binding capacity (TeBC), 17 alpha-hydroxyprogesterone (17-OHP), progesterone (P), thyroxine (T4), thyroid stimulating hormone (TSH), and cortisol were measured, and pubertal stage and bone age were determined. Growth was evaluated according to accepted curves for height and weight. Four of the girls had normal pubertal development, with serum FSH, LH, and E2 levels correlating to the phase of the menstrual cycle. Only one of the girls had ovulatory cycles (increase in P level). The girl treated for EST by abdominal irradiation had gonadal failure, with postmenopausal serum levels of FSH, LH, and E2. Her karyotype was normal. One of the girls was still prepubertal. None of them was hyperandrogenemic. One boy who was treated with bone marrow transplantation and total body irradiation had gonadal failure. One boy was still prepubertal, and the third boy showed normal pubertal maturation and normal serum FSH, LH, and T levels. All the patients except the boy treated with bone marrow transplantation and irradiation were normoprolactinemic; in addition, all had normal thyroid and adrenal function. Height and weight curves were normal in seven of the patients after the cancer therapy. The girl with EST had finished her growth before the irradiation therapy began. The boy treated with bone marrow transplantation and irradiation failed to exhibit further growth after beginning leukemia therapy at the age of 9.3 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum hCG levels measured by time-resolved fluoroimmunoassay in first-trimester pregnancy and after pregnancy termination

Time-resolved fluoroimmunoassay (TR-FIA) reliably shows the concentrations of serum hCG during the first trimester of normal pregnancy. After first-trimester induced abortion the mean disappearance of hCG in serum (under 10 IU/l) takes place in three weeks. TR-FIA is a convenient and ultrarapid method for diagnosing pregnancy-related disorders.

Serum antibody-bound insulin as a measure of insulin antibodies in diabetic children

The usefulness of the measurement of serum antibody-bound and total immunoreactive insulin (IRI) concentrations in the assessment of insulin antibodies was evaluated in a material comprising 49 insulin-dependent diabetic children with a mean age at onset of 8.6 years (range 0.8-16 years) treated with highly purified porcine insulins. Serum antibody-bound and total IRI concentrations of individual patients were compared with insulin antibody levels measured with 3 different insulin antibody assays. The correlation coefficients of insulin antibody levels with concentrations of serum antibody-bound IRI ranged from 0.75-0.79. In serum samples with moderate or high insulin antibody levels most of the insulin was in the form of insulin-insulin antibody immunocomplexes. Thereby a very close correlation was found between antibody-bound and total serum IRI concentrations (r = 0.98) in this material. Residual endogenous insulin secretion decreased with increasing duration of diabetes. No significant correlation was found between the duration of diabetes and serum antibody-bound IRI concentrations. High serum antibody-bound IRI concentrations were associated with low glucagon-stimulated plasma C-peptide levels. Although the determination of serum antibody-bound IRI concentrations does not characterize insulin antibodies with regard to binding capacity and affinity constants, it yields information of the actual degree of insulin binding in the circulation. This information may be useful in assessing the benefits of transferring diabetics with high insulin antibody titers from conventional to highly purified porcine or human insulin therapy.

Sex steroid, gonadotropin, cortisol, and prolactin levels in healthy, massively obese women: correlation with abdominal fat cell size and effect of weight reduction

To examine hormonal status in obese, gynecologically normal women we studied 25 regularly menstruating, massively obese (mean weight, 120 kg) women participating in a weight reduction program and 25 age-matched normal weight (mean weight, 60 kg) women. Serum 17 beta-estradiol (E2), estrone (E1), androstenedione (A), dehydroepiandrosterone sulfate, testosterone, LH, FSH, PRL, and cortisol concentrations were measured during the follicular phase of the menstrual cycle. Waist to hip ratio and abdominal fat cell size were measured at the beginning of the study. The serum levels of E2 (P less than 0.04) as well as those of A, SHBG, and LH (P less than 0.002) were lower in the obese group. Consequently, the testosterone to SHBG ratio and the E1 to A ratio were higher and the LH to FSH ratio was lower in this group. Waist to hip ratio did not correlate with the levels of circulating hormones or SHBG, but an inverse correlation was found between abdominal fat cell size and A as well as the LH to FSH ratio in the nonhirsute women of the obese group. Subsequent to moderate weight reduction (13.2 kg), serum A and E1 levels (P less than 0.01) increased, and serum cortisol levels decreased (P less than 0.001). Thus, massive obesity is associated with abnormalities in hormonal balance in gynecologically symptomless women, there being an association between E1, E2, A, LH, cortisol, and relative weight and/or abdominal fat cell size.

Plasma and urinary C-peptide in the classification of adult diabetics

Plasma and urinary C-peptide determinations in the discrimination between insulin-requiring and non-insulin-requiring diabetes were elevated in 61 adult diabetics. Specimens for C-peptide determinations were taken on two consecutive days: on the first day plasma C-peptide concentrations were determined before and 6 min after intravenous glucagon administration. On the second day 2- and 4-h urinary C-peptide excretion was measured after an individual breakfast. Results of urinary C-peptide analyses were expressed as molar concentration and also as molar quantity excreted (without any corrections and related to creatinine excretion). Glucagon-stimulated plasma C-peptide turned out to be a reliable criterion for the detection of insulin requirement. Sixty-nine per cent of diabetics included in this study were classifiable by basal plasma C-peptide concentrations. Two-hour postprandial urinary C-peptide/creatinine quotient turned out to be slightly less sensitive (89%) than the glucagon test (94%) and of equal specificity (96%). Glucagon-stimulated plasma C-peptide and postprandial urinary C-peptide excretion correlated significantly among insulin-requiring diabetics (r = 0.73), but not among non-insulin-requiring diabetics (r = 0.23). We regard determination of stimulated plasma C-peptide as a primary investigation for the direct assessment of endogenous insulin secretory reserves for clinical management decisions. Determination of postprandial urinary C-peptide is applicable in selected situations for non-invasive assessment of insulin secretion.

Haematological laboratory findings in the elderly: influence of age and sex

The effects of age and sex on haematological laboratory parameters were studied in connection with a population study in people over the age of 65 years (n = 347). Serum vitamin B12 was the only parameter which decreased significantly with advancing age. Blood leucocyte count, haemoglobin concentration, haematocrit, erythrocyte count, mean erythrocyte volume, mean erythrocyte haemoglobin and serum ferritin values were significantly higher in males than in females. Serum iron, serum transferrin, and plasma and erythrocyte folate levels did not differ between males and females. Thirteen subjects were anaemic and three of them had iron deficiency anaemia. Five subjects had iron deficiency based on serum iron and transferrin but no anaemia. Serum ferritin measurement did not reveal any further subjects with iron deficiency. No case of folate deficiency anaemia was revealed. Although many of the participants were on medication, most of them were living at home and taking care of themselves and represent relatively fit elderly people. Therefore we suggest that these laboratory data can also serve as reference values for the elderly people.

C-peptide determination in the choice of treatment in diabetes mellitus

The predictive value of the intravenous glucagon test in assessing the requirement of insulin therapy in diabetes mellitus was evaluated in 105 adult diabetics. Basal and stimulated C-peptide concentrations and increments of C-peptide concentration were examined separately among newly and previously diagnosed diabetics. The poststimulatory C-peptide concentration of 0.6 nmol/l (Novo, antibody M 1230) proved to be the most reliable basis for the choice of therapy. Adequate therapy could have been assessed in 70 cases (67%) without glucagon stimulation. To derive maximal information of plasma C-peptide concentrations, a biphasic scheme of the use for C-peptide determinations and glucagon stimulation is presented. Basal and stimulated C-peptide levels of insulin-requiring diabetics correlated negatively with the duration of diabetes but they did not correlate with the relative body weights. Basal and stimulated C-peptide levels of non-insulin-requiring diabetics did not correlate with the duration of diabetes, but they correlated positively with the relative body weights.

Determination of thyrotropin in serum by time-resolved fluoroimmunoassay evaluated

We evaluated a new, highly sensitive time-resolved fluoroimmunoassay for thyrotropin (TSH) in serum. This direct immunometric "sandwich"-type assay involves two monoclonal antibodies against TSH, one immobilized, the other labeled with europium. Extremely high specific activity of the label and the use of labeled antibody in large excess make the method sensitive enough to measure TSH values falling below the normal reference interval. The standard curve is nearly linear over a wide range of TSH concentrations (standard concentrations range from 0.25 to 324 milli-int. units/L). The lowest concentration detectable was 25 micro-int. units/L. The CV for the assay was less than 6% at 0.5 milli-int. unit/L or higher, 11.3% at 0.1 milli-int. unit/L. For a CV of 10% the lower limit of the working range would be around 0.1 milli-int. unit/L. The interassay CV was 6.7 to 11.8% for TSH concentrations of 0.31 to 19.6 milli-int. units/L. The 95% confidence interval for sera from 111 healthy persons was 0.6-3.8 (range 0.3-3.8) milli-int. units/L. For hyperthyroid patients and thyroid cancer patients treated with thyroxin after thyroidectomy, serum TSH values were all below the reference interval (most were less than 25 micro-int. units/L).

Determination of thyrotropin in serum by time-resolved fluoroimmunoassay evaluated

We evaluated a new, highly sensitive time-resolved fluoroimmunoassay for thyrotropin (TSH) in serum. This direct immunometric "sandwich"-type assay involves two monoclonal antibodies against TSH, one immobilized, the other labeled with europium. Extremely high specific activity of the label and the use of labeled antibody in large excess make the method sensitive enough to measure TSH values falling below the normal reference interval. The standard curve is nearly linear over a wide range of TSH concentrations (standard concentrations range from 0.25 to 324 milli-int. units/L). The lowest concentration detectable was 25 micro-int. units/L. The CV for the assay was less than 6% at 0.5 milli-int. unit/L or higher, 11.3% at 0.1 milli-int. unit/L. For a CV of 10% the lower limit of the working range would be around 0.1 milli-int. unit/L. The interassay CV was 6.7 to 11.8% for TSH concentrations of 0.31 to 19.6 milli-int. units/L. The 95% confidence interval for sera from 111 healthy persons was 0.6-3.8 (range 0.3-3.8) milli-int. units/L. For hyperthyroid patients and thyroid cancer patients treated with thyroxin after thyroidectomy, serum TSH values were all below the reference interval (most were less than 25 micro-int. units/L).

The grade of hirsutism correlated to serum androgen levels and hormonal indices

The degree of hair growth of 64 hirsute women was clinically graded. The patients were divided into two groups with respect to the ratio between the serum luteinizing hormone (LH) and the follicle-stimulating hormone (FSH). The two groups did not differ in terms of the grade of hirsutism, serum testosterone (T), calculated free testosterone (FTc), androstenedione (A), dehydroepiandrosterone sulphate (DHEAS), sex hormone binding globulin (SHBG), estradiol, or cortisol levels. In patients with a LH/FSH ratio of 3.0 or less (n = 49), FTc and A correlated well (rho 0.49, p less than 0.001) to the clinically graded hormonal hirsutism score, while SHBG showed an inverse correlation to it. By contrast, no correlations were found in patients with a serum LH/FSH ratio exceeding 3.0 (n = 15). Various indices for hyperandrogenism were calculated. In patients with lower LH/FSH ratio, T/SHBG, T/SHBG + A/100 and T/SHBG + A/100 + DHEAS/100 showed the best correlation with the clinically scored hair growth. These results show that correlations between hirsutism and hyperandrogenism can be demonstrated.

Acute effect of exogenous thyroxine dose on serum thyroxine and thyrotrophin levels in treated hypothyroid patients

Acute effects of exogenous thyroxine on the serum thyroxine (T4), free thyroxine (FT4) and thyrotrophin (TSH) levels were studied in 20 hypothyroid women during the long-term maintenance therapy. All patients were euthyroid by clinical and laboratory parameters (T4). In nine patients TSH secretion was totally suppressed (less than 1 mu/l) by the mean dose of 178 micrograms thyroxine. Eleven patients had TSH values greater than 1 mu/l. Their mean thyroxine dose (132 micrograms) was not significantly lower than that which totally suppressed the TSH secretion. Ingestion of thyroxine resulted in maximal T4 and FT4 levels at 2 h after taking the drug. Simultaneously TSH concentration reached its minimum. The results indicate that it is necessary to know when the patient has taken the thyroxine in relation to determination of T4, FT4 and TSH levels in order to make the right decisions about the substitution dose of thyroxine. Thus it is essential to take blood sample for hormone determination before the patient ingests the daily thyroxine dose. However, among hypothyroid patients substituted by thyroxine there are individuals whose TSH secretion is not suppressed by normal T4 and FT4 levels.

The effect of antidiuretic hormone, indomethacin and naproxen on prostaglandin synthesis of experimentally infected and healthy kidneys

The authors studied the effect of indomethacin and naproxen on the changes of renal prostaglandin E and F2 alpha concentration in experimental kidney infection, as well as the action of arginine-vasopressin in healthy rats. Naproxen proved to be an effective inhibitor of prostaglandin synthesis, as did indomethacin. In control animals an increased prostaglandin E and F2 alpha synthesis was observed caused by arginine vasopressin. It is supposed that ADH--depending on its concentration--has a metabolic modulator role in prostaglandin synthesis, which raises the possibility of a self-regulatory mechanism of water reabsorption.

Serum oestriol, oestrone and oestradiol concentrations during oral oestriol succinate treatment in ovariectomized women

Serum oestriol, oestrone and 17 beta-oestradiol concentrations during oral oestriol succinate treatment were investigated in ovariectomized women. Either a single dose of 8 mg or two doses of 4 mg were given daily. With the second divided dosage the serum oestriol levels remained uniform. The oestriol concentrations were clearly higher than in the beginning or in the middle of the normal menstrual cycle in the fertile woman. With both treatment schemes the ratio E3/(E2 + E1) was clearly higher than before treatment and during the normal menstrual cycle. Oestriol succinate treatment lowered the ratio E1/(E2 + E3), which was rather similar to the one during normal menstrual cycle.

Termination of pregnancy with double prostaglandin impact

With the "double PG impact" (DPGI) technique in 100 sedated first- and second-trimester volunteers, pregnancy was terminated successfully in 99 with a total extraovular PGF2alpha dose of 19.0 +/- 1.5 mg. in 16.9 +/- 0.9 hours. Two thirds of the patients received only the initial dose of 11.6 +/- 0.5 mg. of PG and aborted in 12.9 +/- 0.7 hours without requiring supplemental treatment. Only mild and transient side effects and 14 indicated curettages were recorded. Excepting one gravida (who failed to abort), plasma progesterone in 99 patients decreased at 3 hours after DPGI from 32.5 +/- 1.7 to 22.7 +/- 1.2 ng. per milliliter (P less than 0.001). The rate of progesterone withdrawal and IAT showed a close relationship and the first-trimester patients aborted at a lower progesterone level than the second-trimester patients (P less than 0.001).

Uterine size measured by ultrasound during the menstrual cycle

In the following study changes in the size of non-pregnant uterus were measured by B-scan ultrasonography. Uterine size in different stages of the menstrual cycle was measured ultrasonically in 16 women, whose periods were confirmed to be ovulatory, both by basal body temperature (BBT) and by the radioimmunological measurement of plasma estradiol and progesterone. It was established that the size of the uterus grows significantly towards the end of the menstrual cycle. In addition to the above mentioned, the examination was performed on a woman of child-bearing age with disturbances in her menstrual cycle. Hormone measurements indicated that her period was anovulatory. No typical uterine growth characteristic of ovulatory cycles could be observed.

Progesterone deficiency and premature labour

Plasma oestradiol 17beta and progesterone levels in 11 patients admitted to hospital for threatened premature labour of unknown aetiology were compared with those of women at similar stages of gestation whose pregnancy was normal. Oestradiol levels in the study group were slightly higher than in the normal controls but their progesterone levels were significantly lower. This progesterone deficiency increased the oestradiol/progesterone ratio in the study group patients, and it increased still more as the progesterone withdrawal continued during premature labour.Since uterine activity during pregnancy is regulated by a balanced action of several factors a deficiency in progesterone, an opponent of uterine activity, creates a regulatory imbalance which, if uncorrected, provokes premature labour. An increase in uterine volume stimulates uterine activity, and the present study reinforced our previous conclusion that the uterine-volume/plasma-progesterone ratio is a more accurate measure of the state of regulatory balance than the progesterone level alone.The cause of the progesterone deficiency in these cases remains unexplained, but we suggest that placental growth and function are contributory factors. We are investigating ways of correcting the resulting imbalance in the regulatory mechanism.