What is the role of the corpus luteum in female reproductive health and how is its function supported?

Corpus Luteum: Role and Function in Female Reproductive Health

Primary Function

The corpus luteum is a transient endocrine gland that produces progesterone to maintain the endometrium for implantation and supports early pregnancy until the placenta assumes steroidogenic function around 8-10 weeks of gestation. 1

Physiological Role and Hormonal Support

Non-Pregnant Cycle

• The corpus luteum develops from residual follicular granulosa and theca cells after ovulation, triggered by the mid-cycle LH surge 2
• It secretes progesterone for 12-14 days during the luteal phase to prepare the endometrium for potential implantation 3
• Without pregnancy, the corpus luteum regresses through PGF2α-mediated luteolysis, causing progesterone withdrawal and menstruation 2

Early Pregnancy Support

• Human chorionic gonadotropin (hCG) from the implanting embryo rescues the corpus luteum from regression, becoming detectable at 6-9 days after conception 1
• The FDA notes that hCG stimulates the corpus luteum to produce progesterone by substituting for LH function, maintaining continued secretion of estrogen and progesterone and preventing menstruation 4
• The corpus luteum remains the primary progesterone source until 8-10 weeks of gestation, when placental steroidogenesis takes over 1
• Peak hCG levels occur at 8-12 weeks, corresponding to the transition period when placental function becomes dominant 1

Clinical Significance Beyond Progesterone Production

Cardiovascular and Systemic Effects

• The corpus luteum contributes to physiological changes in maternal circulation during the luteal phase and early pregnancy beyond simple hormone production 1
• Impaired corpus luteum function represents a potential causal or predisposing factor for preeclampsia, highlighting its broader vascular importance 1

Endometrial Decidualization

• Corpus luteum progesterone drives decidualization—the transformation of endometrium into a receptive state capable of supporting implantation 1
• Defective decidualization from inadequate luteal function has been observed in women who later develop preeclampsia 1

Diagnostic Imaging Characteristics

Ultrasound Appearance

• The American College of Radiology describes the corpus luteum as a <3-cm cystic lesion with a thick wall, with or without internal echoes, or as a rounded hypoechoic lesion 5
• The claw sign—partially surrounding ovarian parenchyma—confirms ovarian origin and distinguishes it from ectopic pregnancy 1
• The corpus luteum appears hypoechoic compared to the hyperechoic rim of a tubal ring in ectopic pregnancy 1

Critical Diagnostic Pitfall

• The corpus luteum is ipsilateral to an ectopic pregnancy in 70-80% of cases, making its presence particularly important when evaluating for ectopic gestation 5, 6
• Both corpus luteum and ectopic pregnancy demonstrate peripheral vascularity on color Doppler, requiring careful attention to location (intraovarian versus extraovarian) for differentiation 1

Management of Luteal Cysts

Conservative Approach

• Luteal cysts are common during pregnancy and typically resolve spontaneously 5
• For cysts >5 cm but <10 cm in premenopausal women, follow-up ultrasound in 8-12 weeks is recommended 5
• Serial hemoglobin monitoring is appropriate for suspected ruptured corpus luteum 5

Key Contraindication

• Fine-needle aspiration of ovarian masses, including corpus luteum cysts, is contraindicated 5

Progesterone Supplementation Considerations

Evidence-Based Indications

• In IVF cycles where normal hormones are suppressed, the corpus luteum does not produce adequate progesterone before the pregnancy test, requiring supplementation 3
• Progesterone supplementation benefits women with bleeding in early pregnancy who have previous miscarriages, possibly through effects on the endometrium or immune system rather than correcting luteal insufficiency 3

Caution Against Overuse

• In recurrent or threatened miscarriage, there is no evidence that the corpus luteum is inherently dysfunctional or that progesterone levels are low 3
• When corpus luteum function appears inadequate, the underlying problem usually involves follicular development or ovulation, and treatment should target these mechanisms 3
• Changes to the hormonal environment in pregnancy may have lifelong consequences for offspring, necessitating restriction of progesterone supplementation to evidence-based indications 3