O hipotireoidismo congênito transitório programa redução de hormônios tireoidianos, hiperleptinemia e hipogonadismo na vida adulta de ratos wistar machos

Abstract

It is known that addition gonadotropinsand testosterone, other hormones are also important to control the reproductive system. Evidences support a pivotal role for both leptin and thyroid hormones (TH) in reproduction. Knowing that disturbances in endocrine status during the neonatal period of life may affect the susceptibility to chronic diseases in adulthood, in this study we used the congenital-neonatal hypothyroidism (CH) as an experimental model to study the influence of hypothyroidism on the adult testicular function and its relation with leptin. So, the aim of this study was to evaluate if adult rats with congenital-neonatal hypothyroidism presented changes in fertility parameters (sperm number, sperm morphology and viability, daily sperm production per testis, and transit time in the epididymis) and in the serum levels of leptin, testosterone, thyroxine (T4) and thriiodothyronine (T3), follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Nine pregnant rats were divided in 3 groups according to the time they received the drug. Group G: free access to water containing 0.03% methimazole (MMI) from day 9 until parturition (D0); group GL: free access to water containing 0.03% MMI from day 9 until 8 days (D8) after parturition and group C: free access to water containing no MMI during all the experimental time. After weaning all male pups (n=8) had free access to pelleted rodent chow and tap water and maintained in groups of up to three/cage until 90 days of age when they were killed by CO2 inhalation. In the adulthood, animals submitted to congenital hypothyroidism presented in relation to C group low levels of T3 (G=10.79% e GL=31.16% p=0.0005), T4 (G=18.69% e GL=20.57%, p=0.0200), LH (G=10.65% e GL=41.28%, p=0.0103), FSH (G=34.24% e GL=44.51%, p=0.0033) and testosterone (G=57.10% e GL=71.17%, p=0.0053) while leptin serum levels (G=17.40% e GL=24.40%, p=0.0093) were high. StAR expression (G=27.03% e GL=22.73%, p=0.0111) and leptin receptors expression in the testis (G=50.79% e GL=52.92%, p=0.0169) was reduced, although it was increased in the epididymis (G=37.90% e GL=40.60%, p=0.0011). Congenital hypothyroidism resulted in a decrease in daily sperm production (G=38.77% e GL=45.03%, p=0.0178), number of spermatid in testis (G=43.17% e GL=48.97%, p=0.0042) and spermatozoa in epididymis cauda (G=29.28% e GL=42.02%, p=p=0.0320) and in the sperm viability (G=11.94% e GL=9.61%, p<0.0031). No statistical difference was seen in the sperm transit time and morphology. In summary, the results reported herein show that congenital hypothyroidism programmed the thyroid function, synthesis and secretion of leptin by adipose tissue and LH secretion by pituitary in the adult animals. Therefore, the animals presented a hypothyroidism condition in adult life associated with reduced steroidogenesis, high leptin serum levels and altered fertility.