Seasons bring about change in hormones, study reveals
The data had been pulled from millions of Israelis between the ages of 20 and 50, with the blood tests sorted by months.
By ZACHARY KEYSERA woman photographs the setting sun on the Spanish island of Ibiza August 29, 2001. Ibiza, one of the most popular tourist attractions in Spain, was hosting the all-night MTV Ibiza 2001 party at Privilege disco which claims to be the largest in the world.(photo credit: REUTERS)
A study of blood samples taken from millions of Israelis over the course of the year reveals that not only do our moods tend to change with the seasons, but also our individual hormone levels.The study, conducted by the Weizmann Institute of Science, used a mathematical tool to uncover patterns in large biological data sets, focusing on differing hormone levels across the seasons.In previous research, study authors Alon Bar and Avichai Tendler, research students at the institute’s Molecular Cell Biology Department, initially focused on the hormone cortisol. They found that it had a dedicated seasonal pattern throughout the year, leading them to set a larger stage to see what other hormones also fluctuate with the seasons.The data had been pulled from millions of Israelis, male and female, between the ages of 20-50. The results for each hormone were averaged from up to six million different blood tests.The researchers tracked 11 hormones, including cortisol, growth hormones and reproductive hormones such as testosterone and estradiol. According to the research, all of the hormones experienced highs and lows over the course of the year, with a "seasonal variation of around 5%."The researchers also discovered that reproductive hormones of both males and females tend to be mirror images of one another, with peaks and dips on the same page throughout the year. This may be the reason why more children are conceived at certain times of the year, according to Bar, adding that it may have more to do with the change in hormone levels than the blooming of spring flowers.Aside from looking into whether hormones change with the seasons, the researchers also created a mathematical model to explain why hormones that are directly related have different dips and peaks throughout the year."Effector hormones such as cortisol and the pituitary hormones, explains Bar, affect not just the body’s metabolism and functions, but the masses of the organs themselves that secrete the hormones," the institute explained in a statement."That is, the pituitary hormones that stimulate the adrenal glands to produce cortisol also cause these glands to grow. But the cortisol produced in the adrenals causes the pituitary to shrink, thus eventually reducing the amount of stimulation to the adrenals, which shrink back down, and so on in a continual loop," the statement said."The dynamic growth and shrinkage of such glands is a known phenomenon, and the researchers were able to link studies measuring the glands to the hormone fluctuations they had observed," it said. "Because the entire process takes place gradually over weeks and months, it creates a time lag from winter to summer and back again, and this explains the differences in peaks between the two groups of hormones."The researchers believe that melatonin is what dictates the year-round clock, and that the patterns they found in the Israeli population would most definitely differ from location to location, as well as a six-month time lag from northern to southern hemispheres."If we saw a 5% difference in Israel, that could be over 15% in Northern Europe,” Bar said."It is not so surprising that our hormones have seasonal cycles,” Tendler said. “Many animals living in temperate climates have strong cycles, for example, all giving birth in the same season."We think that our hormonal systems have ‘set points’ that produce peaks, for example, in stress or reproductive hormones, and these may be adaptations that evolved to help us cope with seasonal changes in our surrounding environment.”
