Ruhayel Yasir, Malm Gunilla, Haugen Trine B, Henrichsen Trine, Bjørsvik Cathrine, Grotmol Tom, Saether Thomas, Malm Johan, Figenschau Yngve, Rylander Lars, Levine Richard J, Giwercman Aleksander
CRC, Department of Clinical Sciences, Lund University, Malmö University Hospital, Malmö, Sweden.
Clin Endocrinol (Oxf). 2007 Jul;67(1):85-92. doi: 10.1111/j.1365-2265.2007.02843.x. Epub 2007 Jun 4.
Seasonal variation in photoperiod or temperature may influence human reproductive biology. The present study evaluated whether seasonal changes occurred in the levels of reproductive hormones and the major melatonin metabolite, 6-sulfatoxymelatonin (aMT6s), in populations exposed to extreme variation in photoperiod and temperature.
Two separate cohorts of Norwegian men were recruited from the general population in either of two locations: Tromsø (69.5 degrees N, n = 92) or Oslo (60 degrees N, n = 112), located north and south of the Arctic Circle (66.5 degrees N), respectively.
Four blood and 12-h overnight urine samples were obtained on separate occasions over a 12-month period, including during the photoperiod maximum and minimum. Serum concentrations of FSH, LH, testosterone (T), oestradiol (E(2)), SHBG and the urinary excretion of aMT6s were assessed.
Statistical analysis using generalized estimating equations indicated that LH levels were lowest during early winter in both locations (both P = 0.01). In Tromsø, free T and E(2) concentrations peaked during early winter (P = 0.02 and 0.003, respectively). In Oslo, free T levels were lowest during early winter (P = 0.06) whereas E(2) levels were lowest during late summer (P < 0.001). Urinary aMT6s concentrations were lowest during early summer in Tromsø and Oslo. Concentrations peaked during early winter in Tromsø (P < 0.001) and during late winter in Oslo (P < 0.001).
LH levels exhibited similar changes in both locations, whereas the patterns of changes of the sex steroid concentrations differed, possibly indicating different underlying mechanisms. Excretion of aMT6s was lowest during early summer in both locations, indicating that the long natural photoperiod was sufficient to cause suppression of melatonin secretion. Whether these changes have any biological significance remains uncertain.
光周期或温度的季节性变化可能会影响人类生殖生物学。本研究评估了在光周期和温度极端变化的人群中，生殖激素水平和主要褪黑素代谢产物6-硫酸氧褪黑素（aMT6s）是否会发生季节性变化。
从挪威男性普通人群中分别招募了两个独立队列，分别来自北极圈（北纬66.5度）以北和以南的两个地点：特罗姆瑟（北纬69.5度，n = 92）或奥斯陆（北纬60度，n = 112）。
在12个月内的不同时间采集4份血液样本和12小时过夜尿液样本，包括在光周期最长和最短期间。评估血清中促卵泡激素（FSH）、促黄体生成素（LH）、睾酮（T）、雌二醇（E₂）、性激素结合球蛋白（SHBG）的浓度以及aMT6s的尿排泄量。
使用广义估计方程进行的统计分析表明，两个地点在初冬时LH水平均最低（P均 = 0.01）。在特罗姆瑟，游离T和E₂浓度在初冬时达到峰值（分别为P = 0.02和0.003）。在奥斯陆，游离T水平在初冬时最低（P = 0.06），而E₂水平在夏末时最低（P < 0.001）。特罗姆瑟和奥斯陆的尿aMT6s浓度在初夏时最低。特罗姆瑟的浓度在初冬时达到峰值（P < 0.001），奥斯陆的浓度在冬末时达到峰值（P < 0.001）。
两个地点的LH水平表现出相似的变化，而性类固醇浓度的变化模式不同，这可能表明存在不同的潜在机制。两个地点的aMT6s排泄量在初夏时均最低，这表明较长的自然光照周期足以抑制褪黑素分泌。这些变化是否具有任何生物学意义仍不确定。
