Prepuberal Expression of Follicle Stimulating Hormone in Mice

Follicle‐stimulating hormone (FSH) is a glycoprotein secreted from the anterior pituitary. Like other glycoproteins, FSH exists as a mixture of isoforms that vary in the number and type of sugar groups. Observed changes in FSH isoforms during critical reproductive events, such as puberty onset, suggest that different combinations of FSH isoforms influence reproduction differently. It has also been suggested that all FSH isoforms may not equally bind to antibody based assays. In order to establish a working model, a study was performed using pre‐pubertal mice to determine at what age FSH mRNA expression begins. Five‐, ten‐, fifteen‐, twenty‐, thirty‐, and sixty‐day‐old mice were sacrificed and FSH expression was determined for the alpha and beta subunits. Both subunits were expressed in all age groups indicating that FSH expression begins very early in development. However, despite the expression of mRNA, morphological studies do not reflect an active form of FSH is initiating gonad development, hormone production, or gametogenesis. Early expression of FSH may be critical to establish a hormonal milieu that leads to maturation of the gonads. Another possibility is that different isoforms of FSH determine its physiological significance during different metabolic states.