EFFECT OF TYROSINE ON SERUM CONCENTRATIONS OF LH,FSH AND TESTOSTERONE IN ADULT MEN

The effect of tyrosine on serum concentrations of LH,FSH and testosterone(T)in 10 adult young men was studied in order to find out whether tyrosine affectsthe secretion of gonadotropins by the pituitary.Five subjects took L-tyrosine orally100mg t.i.d,for 6 days,and five served as control.Blood samples were taken between8:00—9:00 each day for the determination of LH,FSH and T by RIA.On themorning of the fifth day, all subjects were injected intramuscularly with 150μg LRH-A.Blood samples were then obtained 15,30,45,60,90,120,240 min and 24 h afterthe injection.The results showed that tyrosine did not alter both the basic levelsand the LRH-A-stimulated rise of serum LH and FSH,but was capable of increasingthe basic secretion of T slightly.However,tyrosine significantly inhibited theincrease in T concentration which was expected to occur after the LRH-A injection.It is,therefore,believed that tyrosine may exert some inhibitory effect.