Kucharski J

The concentration of GnRH in hypothalamus, LH and FSH in pituitary, LH, PRL and sex steroids in peripheral and ovarian venous plasma of hypo- and hyperthyroid, cysts-bearing gilts

The aim of this work was to investigate the hormonal pattern in hypo- and hyperthyroid gilts with experimentally induced cystic ovarian disease (COD). A total of 70 adult, nulliparous gilts divided into six groups were used for the experiment. Group I was euthyroid and control. Group II was made hypothyroid by oral administration of methylthiouracyl for 24 days. Group III represented euthyroid gilts injected with gonadotropins (PMSG and hCG). Group IV consisted of hypothyroid gilts injected with gonadotropins. Group V was treated with L-thyroxine for 24 days and Group VI with thyroxine and with gonadotropins for the last 10 days of the test. The treatment of all groups was terminated on the 4th-5th day of the next estrous cycle. The peripheral blood of the gilts was collected on Day 0, and on Day 24. On the 25th day the gilts were laparotomized and cannulas were inserted into utero-ovarian veins of each ovary for blood collection. Simultaneously, peripheral blood samples were collected during 1 to 3 consecutive days. The animals were then slaughtered and the hypothalamus, pituitary and ovaries were frozen and preserved for further analyses. In hypothalamic tissue the content of GnRH: in the pituitary the concentration of LH and FSH; and in peripheral and ovarian blood plasma the level of LH, PRL, E1, P4, A4, T and cortisol (Cl) were estimated by RIA procedure. The level of GnRH in the hypothalamus, and LH and FSH in the pituitary showed a tendency to parallel with thyroid function which may indicate a role of this gland in their production or secretion. In hypothyroid animals an increase of LH and PRL and a slight decrease of secretory function of the ovaries were noted. Injections of gonadotropins in euthyroid or hypo- and hyperthyroid gilts intensified the function of the ovaries, which was manifested by numerous follicular cysts and corpora lutea. The hormonal milieu of gilts from these groups showed a low level of LH, PRL and an increased content of sex steroids in peripheral and ovarian blood. The ovarian steroidogenesis of cyst-bearing gilts was disturbed, which was indicated by an increased level of E1, P4, A4, T, and Cl, but a low level of E2. These disturbances in steroidogenesis in cystic gilts may be caused by a deficiency in LH secretion as the consequence of the pituitary gonadotropin suppression by the used gonadotropins. The steroid hormone pattern of cyst-bearing gilts strongly resembles the endocrine profile noted in polycystic ovarian disease in women.