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Related Concept Videos

Hormonal Regulation of the Menstrual Cycle01:22

Hormonal Regulation of the Menstrual Cycle

The ovarian cycle regulates endometrial changes throughout a single menstrual cycle via the coordinated action of gonadotrophin-releasing hormone (GnRH) and gonadotrophins.
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH release.
Hormonal Control of the Ovarian Cycle01:30

Hormonal Control of the Ovarian Cycle

The ovarian cycle is meticulously regulated by the hypothalamic-pituitary-gonadal axis. This cycle orchestrates the release of a mature oocyte, essential for reproduction.
Before puberty, the hypothalamus releases GnRH in a low frequency, low amplitude pulsatile manner. This along with the immature hypothalamic-pituitary-gonadal axis activity, results in low estrogen levels and the absence of a fully functional ovarian cycle.  At puberty, GnRH secretion increases in both frequency and...
Ovarian Cycle01:27

Ovarian Cycle

The menstrual cycle includes a critical component known as the ovarian cycle, which undergoes two main phases each month—the follicular phase and the luteal phase. The follicular phase is variable and averaging around 14 days. Ovulation, triggered by a surge in luteinizing hormone (LH), marks the transition between the two phases. The second phase, the luteal phase, is relatively consistent, lasting approximately 14 days, and is marked by the activity of the corpus luteum. While a cycle length...
Birth Control Methods01:22

Birth Control Methods

Vasectomy is a surgical form of male sterilization that involves severing and sealing the vasa deferentia, preventing sperm from mixing with semen during ejaculation. Because a vasectomy does not impact the testes' ability to produce testosterone, hormone levels, libido, and sexual function generally remain unchanged. While vasectomy is highly effective in preventing pregnancy, with a success rate near 99.85%, rare cases of recanalization (spontaneous reconnection) can occur. Although vasectomy...
Intrauterine Drug Delivery Systems01:21

Intrauterine Drug Delivery Systems

Controlled-release systems for intravaginal and intrauterine drug delivery have been developed primarily for the administration of contraceptive steroid hormones. These delivery routes circumvent first-pass hepatic metabolism, thereby enhancing bioavailability and allowing for reduced systemic dosages compared to oral administration. Such approaches contribute to improved therapeutic efficacy and patient compliance, particularly in long-term contraceptive regimens.Intravaginal Drug Delivery...
Antiplatelet Drugs: Prostaglandin Synthesis, P2Y12 and Glycoprotein IIb/IIIa Inhibitors01:20

Antiplatelet Drugs: Prostaglandin Synthesis, P2Y12 and Glycoprotein IIb/IIIa Inhibitors

Antiplatelet drugs emerge as frontline defenders against the insidious threat of thromboembolic diseases, where abnormal clots obstruct vital blood vessels. These drugs stand as bulwarks, inhibiting platelet aggregation and clot formation, thereby mitigating the risk of life-threatening conditions like myocardial infarction, coronary artery disease, and thrombotic strokes.
Prostaglandin synthesis inhibitors, exemplified by the widely known aspirin, wield their power by irreversibly acetylating...

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Related Experiment Videos

Levonorgestrel administration in emergency contraception: bleeding pattern and pituitary-ovarian function.

Alessandra Tirelli1, Angelo Cagnacci, Annibale Volpe

  • 1Department of Obstetrics, Gynecology and Pediatrics Sciences, Obstetrics and Gynecology Unit, Policlinico of Modena, via del Pozzo 71, Modena, Italy. alessandra.tirelli@unimore.it

Contraception
|April 12, 2008
PubMed
Summary

Emergency contraception (EC) containing levonorgestrel can shorten menstrual cycles if taken before ovulation. Subsequent cycles return to normal, and EC taken after ovulation has no effect on cycle length.

Related Experiment Videos

Area of Science:

  • Reproductive Endocrinology
  • Contraception Research

Background:

  • Levonorgestrel is used for emergency contraception (EC).
  • Its effects on menstrual bleeding and ovarian function require evaluation.

Purpose of the Study:

  • To assess the impact of levonorgestrel EC on bleeding patterns.
  • To investigate effects on pituitary-ovarian function across different cycle phases.

Main Methods:

  • 69 women with regular cycles received EC in follicular, periovulatory, or luteal phases.
  • Hormonal and ultrasound assessments were conducted in a subgroup.

Main Results:

  • EC in the follicular phase shortened cycles by ~11 days.
  • Ovulation was suppressed when EC was given before the LH surge.
  • EC after the LH surge did not affect ovulation or cycle length.

Conclusions:

  • Pre-ovulatory EC inhibits ovulation and shortens the current cycle.
  • Menstrual cycle length normalizes in the following cycle.
  • Post-ovulatory EC does not impact cycle length or ovulation.