Insulin-like growth factor-I, insulin-like growth factor-binding proteins,and gonadotropins in the hypothalamic-pituitary axis and serum of nutrient-restricted ewes

Body condition scores (BCS) of ovariectomized estradiol-treated ewes were c ontrolled to examine effects of suboptimum BCS on insulin-like growth facto r (IGF)-I, ICF-binding proteins (IGFBPs), and LH in the anterior pituitary gland, hypophyseal stalk-median eminence (SME), and circulation. Serum LH i ncreased in ewes with BCS (1 = emaciated, 9 = obese) > 3 (HIGH-BCS), but no t in ewes with BCS less than or equal to 3 (LOW-BCS), after onset of the br eeding season. Concentrations of LH and LH beta subunits in anterior pituit ary glands were lower in LOW-BCS than in HIGH-BCS ewes. Serum IGF-I was low er in LOW-BCS than in HIGH-BCS ewes but did not differ in SME or anterior p ituitary glands. In serum, the 44-kDa IGFBP-3 and 24-kDa IGFBP-4 were lower in LOW-BCS than in HIGH-BCS ewes. In anterior pituitary glands, IGFBP-2 te nded to be higher in LOW-BCS than in HIGH-BCS ewes. In the SME, IGFBP-2, -3 , and -5 were lower in LOW-BCS than in HIGH-BCS ewes. Low body condition ma y inhibit the increased secretion of LH associated with the onset of the br eeding season by altering relative amounts of IGFBPs within the hypothalami c-pituitary axis.