การชักนำให้เกิดภาวะไฮโปไทรอยด์ด้วยยาเมทิมาโซลและความสัมพันธ์ ระหว่างฮอรณ์โมนไทรอกซิน และภาวะการเจริญพันธุ์ในลิงหางยาว (Macaca Fascicularis) เพศเมีย / ยุพาพร ไชยสีหา = Induction of hypothyroidism by methimazole and the interrelationships between thyroxine and fertility in female cynomolgus monkeys (Macaca fascicularis)
This study was aimed to find out whether there are some alterations of serum levels of T₄, E₂ and P and urinary levels of E₁ -3-G and Pd-3∝-G during major stages of menstrual cycle in normal adult female cynomolgus monkeys and whether longterm hypothyroidism induced by an antithyroid drug; methimazole, would have any effect on reproductive endocrinology and associated symptoms. Seven female cynomolgus monkeys which showed regularity of the cycle of 26-35 days were used. RIA determination of thyroid and reproductive steroids during day 3, 10 and 23 of the cycle showed that serum levels of T₄ were 7.3±1.4, 5.1±0.7 and 6.8±1.4Hg/dl; serum E₂ levels were 73.7±32.0, 155.6±44.1 and 80.4±16.1 pg/ml. and serum P levels were 177.5±38.4, 309.7±2.3 and 2578.2±970.0 pg/ml respectively. Urinary levels of E₁ -3-G and Pd-3∝-G were corresponded to endogeneous high levels of E₂ and P in serum during follicular phase and luteal phase respectively. Although there are no significantly different on serum levels of T₄ in all phase of the cycle studied (p<0.05) but T₄ level declined sharply during high endogeneous levels of E₂ in late follicular phase of the cycle. MMI was force fed twice daily. All animals treated with 10 mg/day of MMI showed typical symptoms of hypothyroidism within 2-14 weeks. Those treated with normal range of serum T₄ exhibited normal menstrual cycle and high serum levels of E₂ and P and high levels of urinary metabolites similar to those found in the pretreatment cycles. However when the levels of T₄ was declined to the levels of 1.5-2 Hg/dl, all animals promptly showed cessation of endogeneous E₂ and P productions and showed typical symptoms of menorrhagia, amenorrhea and galactorrhea. When MMI was reduced to the dose of 5 mg/day, serum T₄ and E₂ were slightly increased while serum P was still in low levels. It could be concluded from this study that longterm use of antithyroid drug may have major effect on suppression of both thyroid and ovarian function in cynomolgus monkeys. It is possible that this effect may be exerted via the hypothalamic stimulation of TRH. This hormone may probably stimulate both TSH and PRL from the anterior pituitary gland.
