Abstract
Changes in luteinizing hormone (LH), serum testosterone (T), and salivary T levels with age were examined in Korean men. Serum was obtained from 167 Korean men of different ages ($20{\sim}69\;y$), and the serum LH and T levels were measured. Saliva samples were also obtained, and the salivary T level was determined. The LH levels did not change considerably until 40 y of age (20s, $2.5{\pm}1.0$; 30s, $2.7{\pm}1.5$; and 40s, $2.5{\pm}1.8\;mIU/mL$) but increased significantly around 50 y (50s, $3.7{\pm}1.8$ and 60s, $3.1{\pm}1.7\;mIU/mL$). Further, the serum T levels also did not change until 40 y of age (20s, $5.3{\pm}2.6$, 30s, $4.4{\pm}1.4$, 40s, $4.1{\pm}1.5\;ng/mL$) but decreased significantly at 50 y (50s, $3.4{\pm}1.5$; 60s, $2.6{\pm}0.8\;ng/mL$). The salivary T levels also showed small changes until the age of 40 y ($20s{\sim}40s$, $0.11{\pm}0.015\;ng/mL$) but decreased significantly at 50 y ($0.08{\pm}0.03\;ng/mL$). Thus, the relative ratio of salivary T to serum T levels did not change significantly in all the ages examined ($2.4{\pm}0.9%$). Linear regression analysis predicted that the LH levels increased 1.5%/y while the serum and salivary T levels decreased 1%/y and 0.8%/y, respectively. The serum T/LH ratio did not change considerably until the age of 40 y ($20s{\sim}40s$, $2.27{\pm}0.14$) but decreased significantly ($1.2{\pm}1.0$) at 50 y. Age-related changes in the salivary T/LH ratio were very similar to those in the serum T/LH ratio. These results demonstrated that LH and T levels in serum or saliva did not change considerably until 40 y of age; instead, in Korean men, from 50 y of age, the LH level increased, while the T level decreased. This suggests that primary testicular failure that occurred due to aging (approximately 50 y) and caused this phenomenon. The present study also shows that the salivary T level can be an indicator of the free T level in serum although the salivary T level correlates weakly with the total T level in serum (r=0.53). Thus, information regarding salivary T levels may be useful for studying the age-related changes occurring in male testicular physiology.
한국 남성의 연령 증가에 따른 혈중 luteinizing hormone(LH), testosterone(T), 그리고 타액 T 수준 변화를 조사하였다. 혈중LH 수준은 40대까지 유의한 변화를 보이지 않았으나(20s, $2.5{\sim}1.0$; 30s, $2.7{\sim}1.5$; and 40s, $2.5{\sim}1.8\;mIU/mL$), 50대 이상에서 유의하게 증가하였다(50s, $3.7{\sim}1.8$ and 60s, $3.1{\sim}1.7\;mIU/mL$). 또한, 혈중 T 수준도 40대까지는 변화하지 않았으나(20s, $5.3{\sim}2.6$, 30s, $4.4{\sim}1.4$, 40s, $4.1{\sim}1.5$ ng/mL), 50대 이후 유의하게 감소하였다(50s, $3.4{\sim}1.5$; 60s, $2.6{\sim}0.8\;ng/mL$). 타액 T 수준 또한 40대까지 약간의 변화가 나타났으나($20s{\sim}40s$, $0.11{\pm}0.015\;ng/mL$), 50대에 유의하게 감소하였다($0.08{\sim}0.03\;ng/mL$). 타액 T 대 혈중 T의 상대적인 비율은 모든 연령대에서 유의한 변화가 없었다($2.4{\sim}0.9%$). 직선회귀 분석(Linear regression analysis)에서 혈중 LH 수준은 매년 1.5%씩 증가하고 혈중 T와 타액 T 수준은 각각 매년 1%와 0.8%씩 감소하는 것으로 예측되었다. 혈중 T/LH 비율은 40대까지 유의한 변화가 없었으나($20s{\sim}40s$; $2.27{\pm}0.14$) 50대에 유의하게 감소하였다($1.2{\sim}1.0$). 연령과 관련된 타액 T/LH 비율은 혈중 T/LH 비율과 대단히 유사하였다. 본 연구 결과에서 혈중 LH와 T, 그리고 타액 T 수준이 한국인 남성에서 40대까지는 유의하게 변화하지 않았고, 50대부터는 LH 수준이 증가하고 T 수준이 감소하였다. 이 결과는 50대경 노화과정에 의해 일어나는 원발성 정소부전(primary testicular failure)이 원인인 것으로 보인다. 또한, 본 연구결과는 비록 타액 T 수준이 혈중 총 T 수준과 약한 상관관계(r=0.53)를 갖지만, 혈중 free T 수준을 나타내는 것으로 보인다. 그러므로, 타액 T 수준에 대한 정보는 연령과 관련해서 나타나는 남성 정소생리를 연구하는데 유용할 것으로 사료된다.
(Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University)