Progesterone and Luteinizing hormone secretion patterns in early pregnant gilts

Area of Science:

• Reproductive Endocrinology
• Swine Reproduction

Background:

• The corpus luteum (CL) is crucial for maintaining pregnancy through progesterone secretion.
• Luteinizing hormone (LH) plays a role in regulating ovarian function and CL activity.

Purpose of the Study:

• To investigate the relationship between luteinizing hormone (LH) pulsatility and episodic progesterone release from the CL in gilts.
• To determine if LH pulses precede or influence progesterone release during early pregnancy.

Main Methods:

• Blood samples were collected every 15 minutes for 12 hours on Days 11 and 21 post-insemination from pregnant and non-pregnant gilts.
• LH and progesterone levels were analyzed for basal concentrations, mean levels, pulse frequency, and pulse amplitude.
• Pregnancy status was confirmed at euthanasia.

Main Results:

• Progesterone parameters did not differ between pregnant and non-pregnant gilts on Day 11.
• In pregnant gilts, both progesterone and LH pulse amplitude significantly declined from Day 11 to Day 21.
• No progesterone pulse followed an LH pulse within one hour on Day 21, indicating a lack of direct short-term causality.

Conclusions:

• Progesterone pulses in gilts do not directly follow LH pulses within a one-hour timeframe during early pregnancy.
• Successful CL formation is independent of progesterone release on Day 11 post-insemination.
• The decline in progesterone from Day 11 to Day 21 is associated with decreased progesterone pulse amplitude and frequency, coinciding with a decline in LH pulse amplitude.