Insulin-like growth factor-I as a follicular growth promoter during early pregnancy in thoroughbred mares.

The research focuses on understanding the physiological role of the insulin-like growth factor-I (IGF-I) during early pregnancy in thoroughbred mares, indicating that IGF-I may be produced from medium and large follicles and help in their growth during the first trimester.

Research Method

• The researchers observed the number of ovarian follicles during different stages of the first trimester of pregnancy in a sample of 36 thoroughbred mares through ultrasonic monitoring.
• In 9 out of the 36 mares, they regularly collected blood samples from the mating day until the end of the first trimester.

Data Analysis

• The team studied plasma IGF-I profiles along with other hormones like the follicle stimulating hormone (FSH), luteinizing hormone (LH), ir-inhibin, progesterone, and estradiol-17beta.
• They noticed that the plasma IGF-I levels fluctuated during the period of study, with peaks on the 7th, 28th, 49th, and 84th days of pregnancy.

Findings

• Plasma IGF-I was noticed to have a positive correlation with plasma FSH, but no correlation was evident with the other hormones during this period of study.
• Plasma IGF-I did not show a correlation with the foetal size, yet a positive correlation with the number of large (>30 mm) and medium (10-30 mm) follicles was noted.
• This suggest that the IGF-I might be produced from medium and large follicles in the early pregnancy and could potentially contribute to their development via pituitary FSH mediated effects.