HPL levels as a guide to foetal well-being during pregnancy - Medical Monograph 8 - The Radiochemical Centre, Amersham England

Sep 21, 2026

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Human placental lactogen (HPL) is presented as a protein hormone synthesized by the placental syncytiotrophoblast and detectable early in pregnancy, with rapidly increasing production in the last trimester and very high circulating concentrations near term. Because HPL levels largely reflect placental functional mass and show limited physiological control, they are discussed as a clinical guide to foetal well-being. The monograph covers terminology, physiology, radioimmunoassay measurement, placental function testing criteria, normal and abnormal pregnancy patterns, and future developments.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages24

Reading Time1 h 0 min

AccessFree to download

Introduction

Nomenclature

Physiology of HPL

Measurement of HPL

Criteria of a placental function test

Circulating HPL levels in normal pregnancy

Circulating HPL levels in abnormalities of pregnancy

Discussion

Conclusion

Future developments

References

HPL levels as a guide to foetal well-being during pregnancy Medical Monograph 8 The Radiochemical Centre Amersham England Human placental lactogen levels as a guide to foetalwell-being during pregnancy T.Chard MD MRCOG Senior Lecturer in Reproductive Physiology,St.Bartholomew'sHospital Medical College,London,ECIA 7BE The Radiochemical Centre,Amersham,England Contents | Introduction | 5 | | --- | --- | | Nomenclature | 5 | | Physiology of HPL | 5 | | Measurement of HPL | 7 | | Criteria of a placental function test | 7 | | Circulating HPL levels in normal pregnancy | 8 | | Circulating HPL levels in abnormalities of pregnancy
Abortion | 10 | | | Il | | Pre-eclampsia and hypertension | |I | | Erythroblastosis | 13 | | Diabetes in pregnancy | 13 | | Placental insufficiency | 14 | | Foetal distress and neonatal asphyxia | 15 | | Discussion | 15 | | Conclusion | 16 | | Future developments | 17 | | References | 18 | # Introduction Since the 1930's it has been known that the placenta of severalmammalian species synthesizes and releases a protein hormone withlactogenic properties.In 1962 and 1963,the now classical work ofJosimovich(1-2)demonstrated that the lactogenic protein of the humanplacenta bears a close immunological similarity to pituitary growthhormone,a finding which was closely followed by the development ofthe first specific radioimmunoassay for this hormone(3).Subsequentwork has fully confirmed the original concept,and has includeddetailed investigation on the chemistry,physiology and pathophysi-ology of human placental lactogen,much of the interest centring onthe possibility that its circulating levels may be an excellent guide tofoetal well-being during pregnancy. # Nomenclature 'Human placental lactogen'(HPL)was the name originally suggested byJosimovich.A number of other names have been put forward,including 'chorionic growth hormone prolactin'(CGP),‘purifiedplacental protein'(PPP),and 'human chorionic somatomammotrophin'(HCS).At a recent meeting at the Ciba Foundation(4),a group ofdistinguished workers in the field decided the simplest and mostacceptable name was human placental lactogen (HPL),and this termwill be used here. # Physiology of HPL HPL is a protein with a structure very similar to that of human growth hormone(5.It is synthesized by the syncytiotrophoblast of theplacenta(⁶)and is detectable from an early stage of pregnancy.In thelast trimester,the amount synthesized is of the order of lg perday(7),a rate of production greatly in excess of that of any otherpeptide hormone.Indeed,a woman in the last month of pregnancywill secrete more HPL than she will of insulin in her entire life.Thehigh rate of production,coupled with a half-life of the order of 10-20minutes(⁸),explains the very high circulating levels which at term areof the order of 6μg/ml of plasma. HPL is secreted mainly into the maternal circulation,and in thefoetus itself the levels are some two orders of magnitude less(3).It ismetabolized in the liver and the kidneys,although only a small fractionis excreted in the urine.It also appears in amniotic fluid,at levelsaround one-tenth of those found in the maternal circulation. The physiological functions of HPL are virtually unknown.In contrastto growth hormone,it has little somatotrophic action(9),and itsmammotrophic and lactogenic effects are less than those of pituitaryprolactin.It has been suggested that it is responsible for the well- Figure 1. # The synthesis and distribution of HPL in late pregnancy. known diabetogenic effect of pregnancy,and that this function adjustsglucose and fat metabolism in favour of the foetus.However,sinceboth oestrogens and progesterone may have a similar effect,it isdifficult to attribute a specific function to HPL in this respect.As withthe placental steroids,there appears to be a high level of syntheticactivity with no obvious purpose. The absence of a we

FAQs

What is human placental lactogen (HPL) and where is it produced during pregnancy?

HPL is a protein hormone synthesized by the placental syncytiotrophoblast and becomes detectable from early pregnancy onward. It is mainly secreted into the maternal circulation.

Why are HPL circulating levels used as a guide to foetal well-being?

The text links HPL levels to placental functional mass because synthesis and release appear largely autonomous. Consequently, circulating HPL levels can reflect the placenta’s ability to support pregnancy.

How is HPL measured in the monograph?

Most studies rely on radioimmunoassay. The monograph explains how the assay differs from those for comparable materials like growth hormone and discusses why high sensitivity is not required.

Sep 21, 2026

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