Protein hormones are similarbut not necessarily identical withthose produced by the pituitary. Forexample placental lactogen ischemicaly similar to both pituitarygrowth hormone and prolactin, butbiological activity of placentallactogen is much inferior thanprolactin or growth hormoneproduced by pituitary.
Human chorionic gonadotrophinHuman placental lactogenPregnancy specific β-1 glycoprotein (PSβ-1G)
hCG is a glycoprotein Molecular weight is 36000-40000 daltons It consists of a hormone non-specific α(92 amino acids) and a hormone specific β(145 amino acids) subunit The α subunit is biochemically similar to LH, FSH and TSH Β subunit is relatively unique to hCG
It act as a stimulus for the secretion of progesteron by the corpus luteum of pregnancy The rescue and maintenance of corpus luteum till 6 weeks of pregnancy It stimulate Leyding cells of the male fetus to produce testosterone It has got immuno-suppressive activity
It inhibit the maternal process of immunorejection of the fetus as a homograftStimulates both adrenal and placental steroidogenesisStimulates maternal thyroid because of its thyrotrophic activity
The half life of hCG is about 24 hours By radioimmunoassay it can be detected in the maternal serum or urine as early as 8-9 days following ovulation The doubling time of hCG concentration in plasma is 1.4-2 days It reach maximum levels ranging 100IU and 200IU/ml between 60-70 days of pregnancy The concentration falls slowly reaching a low level of 10-20IU/ml between 100-130 days There after it remains constant throughout pregnancy Slight secondary peak occur at 32 weeks Hormone disappears from the circulation within 2weeks following delivery
Multiple pregnancyHydatidiform mole or choriocarcinomaPregnancy with a21 trisomy fetus
Itis synthesised by the syncytiotrophoblat of the placenta. Chemically and immunologically similar to pituitary growth hormone and prolactin. HPL in maternal serum is first detected during the 5th week. The level rises progressively from 5micro gms/ml to 25micro gms/ml until about 36 weeks. The plasma concentration of HPL is proportional to placental mass.
Antagonizes insulin actionHigh level of maternal insulin helps protein synthesisHPL causes lipolysis and proteolysisPromotes transfer of glucose and amino acids to the fetus.
Produced by the trophoblast cells It can be detected in the maternal serum 18—20 days ovulation. PS β– 1 G is a potent immunosupressor of lymphocyte proliferation It prevents the rejection of the conceptus
Early pregnancy factor (EPF)is a protein ,produced by the activated platelets and other maternal tissues. It is detected in the circulation 6 to 24 hours after conception. It is an immunosupressant and prevents rejection of the conceptus.
Inhibin , activin, insulin like growth factor, transmitting growth factor β and epidermal growth factors are produced by the syncytiotrophoblast cells.Functios include, Immunosupressive Paracrine Steroidogenic.
A (PAPP-A) is secreted by the syncytiotrophoblastIt act as an immunosupressant in pregnancy
OESTROGEN: The site of production is in the syncytiotrophoblastChemical nature: Estrogens are phenolic steroids with 18 carbon atoms, charecterized by an atomic ring.Estriol is produced in large amounts during pregnancy.
Maternal cholesterol is converted in by placenta to pregnenolone and later to progesterone. Placental pregnenolone toghether with fetal adrenal pregnenolone is partly converted to pregnenolone sulphate . pregnenolone sulphate is then coverted by fetal adrenals to dehydroepiandrosterone sulphate or DHEA SO4 ,the most important percurser of placental oestrogens. This biochemical changes is produced by hydrolysis of the sulphate to dehydroepiandrosterone and conversion to androsterone, followed by aromatization of oestrogen.
DHEA SO4 of fetal adrenal origin is converted in the fetal liver to 16- alpha hydroxy DHEA SO4 which is then converted by placenta to oestriol in two steps. Step 1: Sulphatase removes the so4 radical. Step 2: Aromatase converts the A ring to the phenolic stucture characteristics of oestrogens. Thus the production of oestriol involves the integration of maternal , fetal and placental pathways.
Oestriol is first detectable at 9weeks (0.05ng/ml) and increases gradually to about 30ng/ml at term.
Normal oestriol value values signify fetal well- being. Oestriol levels reflects placental functioning ability. Low oestriol level indicates , fetal death, fetal anomalies (adrenal atrophy, anencephaly, down syndrome), hydatidiform moles, placental sulphatase or aromatase deficiency. High levels are often associated with multiple pregnancy and Rh-isoimmunization. Declining oestriol levels or their failure to rise on serial examinations are indicative of placental insuffiency causing IUGR, PIH, maternal renal disease.
Before 6weeks of pregnancy thecorpus luteum secretes 17-hydroxyprogesterone. Following the development oftrophoblast it is synthesised and secretedform placenta. The placenta can utilisecholesterole as a precuser derived from themother for the production of pregnenoloneand ultimatly progesterone.
The average levels of progesterone at 12week ,28week, and term approximate 25ng/ml, 80ng/ml, 300ng/ml respectively. Low progesterone levels are observed in ectopic pregnancy and abortion. High values are observed in , hydatidiform mole, Rh-isoimmunization. After delivery plasma progesterone level decreases rapidly and is not detectable after 24 hours.
Oestrogen causes hypertrophy and hyperplasia of the uterine myometrium. Progesterone in conjunction with oestrogen stimulates growth of the uterus It causes decidual changes in the endometrium and inhibits myometrial contraction. Hypertrophy and proliferation of breat ducts are due to oestrogen Both steroids are required for the adaptation of the maternal organs to the constantly increasing demands of the growing fetus.
Oestrogen sensitises the myometrium to oxytocin and prostaglandins. Oestrogen ripen the cervix. Progesterone along with hCG and decidual cortisol inhibits T-lymphocyte mediated tissue rejection and protects the conceptus. Together they cause inhibition of cyclic fluctuating activity of gonandotropin-gonadal axis ther by preserving gonannnnndal function
Diagnosisof pregnancy Follow up cases who had trophoblastic tumours Detection of functions of feto-placental unit
Main source of production is the corpus luteum of overy,but part of it may be produced by the placenta and decidua. Relaxin relaxes the symphysis and sacroiliac joints during pregnancy and also helps in cervical ripening by its biochemical effect.