Enhancement of seminiferous tubular growth and spermatogenesis in testes of rats recovering from early hypothyroidism: a quantitative study

Abstract

Testicular weight and DNA content were markedly reduced (63 and 69%) in weanling Long-Evans rat pups rendered hypothyroid from birth by administration of propylthiouracil (PTU), a reversible goitrogen. These growth deficits worsened to > 80% by continuing hypothyroidism beyond weaning, to days 50 and 90. Recovery of thyroid function, brought about by discontinuing PTU at weaning, resulted in a paradoxical stimulation of testis growth, amounting to increased weight (40%), DNA content (60%) and size by 90 days, compared to age-matched controls. In the 25-day or older hypothyroid rats, testicular structure was immature and spermatogenesis markedly delayed, as evident by closed lumen and significantly reduced diameter of seminiferous tubules (38%), thickness of germinal layer (70%), and number of primary spermatocytes (86%), compared to control. Hypothyroidism did not alter the number of tubules per testis cross section. In the 90-day recovery rats, numbers of seminiferous tubules were unchanged but tubular diameter was significantly (20%) larger than in controls and spermatogenesis appeared very active as indicated by significantly increased germinal layer thickness (22%) and total number and density of primary spermatocytes (55% and 40%). The results show that although postnatal hypothyroidism is deleterious for testicular growth and spermatogenesis, recovery from this condition leads to enhanced seminiferous tubular growth and spermatogenesis.

Developmental Hormonal Profiles in rdw Rats with Congenital Hypothyroidism Accompanying Increased Testicular Size and Infertility in Adulthood

“…This observation contradicted that of previous reports on transient hypothyroidism [10][11][12] and chronic hypothyroidism in rats [14].…”

“…This means that rdw rats are hypothyroid but not in the phase of deprivation. Chronic hypothyroidism caused by PTU treatment from birth to 90 days was reported to severely suppress testicular growth [14]. In transient neonatal PTU-treated rats, serum T4 levels increase from 30 days of age until normal levels are reached after about 20 days [19] and this elevated T4 may accelerate the increase of Sertoli cell number [27,34].…”

“…Increased testis weight occurs in adulthood accompanied by fertility and an increase of sperm number when neonatal transient hypothyroidism is induced in rats by anti-thyroid hormones such as 6-propyl-2-thiouracil (PTU) [10][11][12], or polychlorinated biphenyl (PCB), which is a typical environmental hormone [13]. Chronic hypothyroidism in rats given PTU for long periods after birth until the adult age causes atrophy of the testis and induces infertility [14]. Thus, the size or weight of the testis usually seems to correspond well with male sexual activity in neonatally transient or chronic hypothyroidism as well as in seasonal breeders such as rams [15] and minks [16].…”

Investigation on the Histopathological Effects of Thyroidectomy on the Seminiferous Tubules of Immature and Adult Rats

“…Early studies indicated that transient neonatal hypothyroidism induced by the administration of PTU causes the considerably reduced tubular diameter in immature rats [11,15]. For example, Meisami et al [15] found that neonatal hypothyroidism resulted in a significantly reduced diameter of the seminiferous tubules (38%) and thickness of the germinal layer (70%) in immature rats.…”

Effect of Selenium on Carbimazole-Induced Histopathological and Histochemical Alterations in Prostate of Albino Rats

“…Szanto et al [27] found that propylthiouracil decreased both hepatic receptor-related protein and low-density-lipoprotein receptor expression in rats. Meisami et al [28] reported that testicular weight and DNA content were markedly reduced in rat pups administered by propylthiouracil. Carbimazole administration caused a significant decrease of the proliferation, nucleic acids and protein synthesis of the thyroid follicular and adrenocortical cells [29].…”