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Hormonal Control of the Ovarian Cycle

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...

Hormonal Regulation of the Menstrual Cycle

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.

Oogenesis

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...

Oogenesis

Oogenesis

Oogenesis, the process of developing egg cells (female gametes), occurs within the ovaries and is fundamental to female fertility. This sequence begins during fetal development when diploid oogonia in the developing ovaries undergo mitotic divisions to produce primary oocytes. By birth, these primary oocytes enter prophase I of meiosis but become arrested in this stage, remaining suspended until puberty.
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is known...

Ovarian Cycle

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...

Gonadal and Placental Hormones

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The gonads, namely the testes in males and the ovaries in females, are pivotal in producing gonadal hormones that orchestrate the intricate processes of sexual development and reproduction.
In males, testosterone is the primary gonadal androgen. It plays a central role in the maturation of male reproductive organs — the penis and testes. Additionally, testosterone is instrumental in the development of secondary sexual characteristics — a deep voice as well as facial and pubic hair growth — and...

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Updated: Jun 20, 2026

A Modified Technique for Inducing Polycystic Ovary Syndrome in Mice

A Modified Technique for Inducing Polycystic Ovary Syndrome in Mice

Published on: July 5, 2024

Endocrinologic control of normal canine ovarian function.

P W Concannon¹

¹Department of Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. pwc1@cornell.edu

Reproduction in Domestic Animals = Zuchthygiene

|September 17, 2009

Summary

This summary is machine-generated.

Canine reproduction involves follicle selection during anoestrus, triggered by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The corpus luteum

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Area of Science:

Reproductive Endocrinology
Canine Physiology
Animal Reproduction

Background:

The canine estrous cycle is characterized by a prolonged anestrus period (3-10 months).
Follicular development and selection are crucial for initiating the cycle.
Hormonal regulation of the canine corpus luteum differs from other species.

Purpose of the Study:

To elucidate the hormonal mechanisms regulating the termination of anestrus in dogs.
To describe the endocrine and paracrine events during the canine estrous cycle, including pregnancy.
To understand the lifespan and regression of the canine corpus luteum.

Main Methods:

Analysis of hormonal concentrations (LH, FSH, estradiol, progesterone, prolactin) during different stages of the canine estrous cycle.
Observation of follicular dynamics and corpus luteum function.
Comparison of reproductive events in pregnant and non-pregnant bitches.

Main Results:

Termination of anestrus is driven by increased LH pulse frequency, stimulating estradiol production from FSH-primed follicles.
The canine corpus luteum has a genetically programmed lifespan, influenced by LH and prolactin.
Progesterone secretion during pregnancy is enhanced by prolactin, with luteolysis occurring pre-partum via prostaglandin F.
Changes in plasma volume and metabolism affect serum progesterone levels during pregnancy.

Conclusions:

The canine estrous cycle is precisely regulated by complex hormonal interactions.
Understanding these mechanisms is vital for reproductive health and management in dogs.
The canine model offers unique insights into luteal phase regulation and lifespan.