Effect of transient early hyperthyroidism on onset of puberty in Suffolk ram lambs

Abstract

The thyroid function and sexual development of eight 6-week-old Suffolk ram lambs were studied. The lambs were divided into either control or treatment groups and housed indoors. From 6 to 12 weeks of age, four lambs in the treatment group received 15 mg kg(-1) body weight per day of 6-propyl 2-thiouracil orally to suppress normal thyroid function. During the same period, thyroxine and tri-iodothyronine were injected s.c. at the rate of 8 and 16 microg kg(-1) body weight per day, respectively, to induce a hyperthyroid state. Four control lambs received sham injection and oral excipient. Concentrations of thyroxine, tri-iodothyronine, FSH, testosterone and insulin-like growth factor I were determined in blood collected by indwelling jugular catheters once a week, every 20 min from 09:00 to 15:20 h. Scrotal circumference was recorded each week. Semen collection was attempted by electro-ejaculation between weeks 17 and 36. Lambs were castrated at week 36 and testicular histology was examined. During the treatment period only, the concentration of thyroid hormones was higher in treated lambs than in controls (P < 0.05). From week 6 to week 9 only, concentrations of FSH in treated lambs were lower than in controls (P < 0.05). Insulin-like growth factor I concentrations were lower in treated lambs than in controls from week 10 to week 13 (P < 0.05). Frequency of testosterone pulses was higher (P < 0.01) in the treated lambs but concentrations were similar in the control and treated lambs throughout the experiment. Scrotal circumference was greater in treated lambs from week 26 to week 36 (P < 0.05). Treated lambs produced viable spermatozoa earlier than did control lambs. At week 36, sperm concentration in treated lambs was higher than in controls (P < 0.01) but semen volumes were similar (P > 0.1). Diameter of the seminiferous tubules in treated lambs was larger than in controls (P < 0.05). In conclusion, transient neonatal hyperthyroidism decreased FSH and insulin-like growth factor I concentrations temporarily, increased testosterone pulses and sperm production and advanced puberty in Suffolk ram lambs.

Experimental research Maturational changes in connexin 43 expression in the seminiferous tubules may depend on thyroid hormone action

“…A decrease in body weight indicated a thyrotoxic effect of high T3 level. Follicle-stimulating hormone (FSH) is responsible for seminiferous tubule growth [27], and it was previously found that in pubertal ram lambs, T3 administration decreased serum levels of FSH [28]. In our study, FSH level did not differ from earlier reports incorporating a rat model [7].…”

A Deep Insight of Spermatogenesis and Hormone Levels of Aqua-Cultured Turbot (Scophthalmus maximus)

“…In the early 21st century, T3 was revealed to regulate the growth and maturation of the testis of mammals, including influencing the proliferation and differentiation of Sertoli cells and Leydig cells (Holsberger et al, 2005;Mendis-Handagama and Siril Ariyaratne, 2005). T3 also participates in the steroidogenesis (e.g., the synthesis of T and E2) (Maran et al, 2000;Fallah-Rad et al, 2001;Hernandez, 2018). For a long time, T3 is mainly recognized to function during early testis development at prepubertal age.…”

“…In contrast, there are more reports of hormones during fish reproduction, including studies on sex steroids (e.g., androgen, estrogen, and progesterone) (Weltzien et al, 2002;Miura et al, 2006;Schulz et al, 2008Schulz et al, , 2010Björn et al, 2013;Chen et al, 2013;Hachero-Cruzado et al, 2013;O'Shaughnessy, 2014;Chauvigné et al, 2016Chauvigné et al, , 2017Hyeon et al, 2019), and other hormones [e.g., thyroid, and 5-hydroxytryptamine (5-HT)] (Bertil, 1994;Fallah-Rad et al, 2001;Holsberger et al, 2005;Mendis-Handagama and Siril Ariyaratne, 2005;Kreke and Dietrich, 2008;Wagner et al, 2008;Munakata and Kobayashi, 2010), which all involved in the spermatogenesis and the maintenance of male function. These works have provided us with ideal candidates in studying the regulation of steroid hormones during spermatogenesis.…”

The Intergenerational Impacts of Paternal Diet on DNA Methylation and Offspring Phenotypes in Sheep

“…Several of the genes associated with DMRs are linked to the sertoli cell function. The number of sertoli cells controls testis size and rate of sperm production (Fallah-Rad et al, 2001;Aponte et al, 2005). The biological window during which most Sertoli cells undergo proliferation is the prepubertal stage (Buzzard et al, 2000).…”

“…The relationship between body weight and thyroid hormone status is well established (Knudsen et al, 2005;Iwen et al, 2013;Fox et al, 2019). Further, thyroid function is a marker for both early and delayed puberty in humans (Klein et al, 2017) and sheep (Fallah-Rad et al, 2001), and is a regulator of Sertoli cell proliferation (Holsberger and Cooke, 2005). Thyroid hormone also serves as a modulator of bone acquisition during prepubertal growth (Xing et al, 2012).…”