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What is the cause of yellow semen syndrome (YSS)?

Do you have yellowish ejaculate?

  • Yes

    Votes: 4 57.1%
  • No

    Votes: 2 28.6%
  • Only after a long time of sexual abstinence.

    Votes: 1 14.3%

  • Total voters
This is basically a meta-analysis of PubMed articles containing the terms "yellow semen".

Of course these are all studies performed on animals (13 on wild turkeys (Meleagris gallopavo), 1 on an American Quarter Horse, 1 on Angora goats and 1 on Holstein Friesian bulls).

My goal is to find out the cause of yellowish semen in men but due to the lack of studies on humans I will take these animals studies.

When you search on the internet for the cause of yellowish semen you will always find the same answer: Either it is claimed as a normal deviation from the norm without any effect on sperm motility or it is caused by aging.

Doctors tend to declare symptoms as normal when just enough percentage of the population experience them.

But the fact is yellowish semen is abnormal and this post is not about other causes of yellow semen as sexually transmitted infections (STI).

I personally can definitely exclude STI as a cause (just think of the movie The 40-Year-Old Virgin lol).

But I don't exclude other pathogens like viruses, bacteria or protozoa.

Now I will do conclusions of the 16 studies ranging from 1960 to 2018.

Br Poult Sci. 2018 May 31. doi: 10.1080/00071668.2018.1483576. [Epub ahead of print]
Differences in aromatase expression and steroid hormone concentrations in the reproductive tissues of male domestic turkeys (Meleagris gallopavo) with white and yellow semen.
Pardyak L, Kaminska A, Brzoskwinia M, Hejmej A, Kotula-Balak M, Jankowski J, Ciereszko A, Bilinska B.

Conclusion: An up-regulation of aromatase (an enzyme that converts testosterone to estrogen) and estrogen receptor alpha (ERα) was found in testicles, epididymis (the smaller attachment to the testicles) and ductus deferens (that's the duct connecting the testicles to the prostate and urethra) compared to white normal semen (WNS) suibjects.
Testosterone concentration diminished in YSS epididymis and ductus deferens, but not in the testes. Concomitantly, increased oestradiol concentration was found in YSS testes and epididymis but decreased in the ductus deferens.

Poult Sci. 2018 Mar 1;97(3):1059-1065. doi: 10.3382/ps/pex366.
Metabolomic analysis of white and yellow seminal plasma in turkeys (Meleagris gallopavo).
Slowinska M, Sallem H, Clench MR, Ciereszko A.

Conclusion: Significant changes in the levels of metabolites were detected in yellow vs. white seminal plasma. Significantly differentiated metabolites were subjected to Ingenuity Pathway Analysis. Lipid metabolism, molecular transport, and nucleic acid metabolism were the top pathways that differentiated white and yellow seminal plasma.
These data strongly suggest that disturbance of carbohydrate and lipid metabolism is characteristic for YSS. The abnormal metabolism of lipids may contribute to the numerous lipid vacuoles previously observed in the reproductive tracts of YSS males. An increased level of riboflavin in YSS may be responsible for yellow turkey semen pigmentation.
A disturbance in thyroid hormone metabolism visible at protein and metabolic levels may be involved in YSS in turkey.

J Anim Sci. 2015 Jun;93(6):2785-95. doi: 10.2527/jas.2015-8912.
Proteomic analysis of white and yellow seminal plasma in turkeys (Meleagris gallopavo).
Słowińska M, Kozłowski K, Jankowski J, Ciereszko A.

Conclusion: A total of 49 protein spots (30 upregulated and 19 downregulated) were differentially expressed in yellow seminal plasma compared with white seminal plasma. Transthyretin and serum albumin-like showed a 3-fold increase in seminal plasma from males with YSS, and the latter was validated using Western blot analysis.
A 3-fold increase was observed for hemopexin-like and immunoglobulin light chain V-J-C region. Pantetheinase-like showed a 1.3-fold increase. Ovotransferrin, hepatocyte growth factor activator, cysteine-rich secretory protein 3-like, and ferritin heavy chain-like showed a significant decrease (at least a 1.3-fold decrease) in yellow semen.

J Vet Diagn Invest. 2012 Jul;24(4):801-3. doi: 10.1177/1040638712447936. Epub 2012 May 23.
Isolation of Equine rhinitis A virus from a horse semen sample.
Johnson DJ, Ostlund EN, Palmer TJ, Fett KL, Schmitt BJ.

Conclusion: Could a virus cause yellow semen? The study says that the semen was likely contaminated with urine, so it is rather useless.

Poult Sci. 2011 Jan;90(1):181-90. doi: 10.3382/ps.2010-00956.
Effect of organic and inorganic forms of selenium in diets on turkey semen quality.
Slowińska M1, Jankowski J, Dietrich GJ, Karol H, Liszewska E, Glogowski J, Kozłowski K, Sartowska K, Ciereszko A.

Conclusion: Yellow semen was characterized by increased biochemical parameters and decreased spermatozoa motility characteristics. However, the percentage of motile spermatozoa did not differ between white and yellow semen.
Increased superoxide dismutase activity can be used as an indicator of yellow semen.

Some bacteria produce SOD to protect themselves from superoxides.

Source: Microbiology. 2011 Aug | Superoxide dismutase C is required for intracellular survival and virulence of Burkholderia pseudomallei. | Vanaporn M, Wand M, Michell SL, Sarkar-Tyson M, Ireland P, Goldman S, Kewcharoenwong C, Rinchai D, Lertmemongkolchai G, Titball RW | https://www.ncbi.nlm.nih.gov/pubmed/21659326

"Apart from targeting NADPH assembly and activation, many pathogens express enzymes that neutralize ROIs. L. monocytogenes [S73], Salmonella [18], Yersinia [S74], F. tularensis [S75], and Mtb [S76,S77] all express surface-associated and cytoplasmic superoxide dismutases, which scavenge superoxide radicals. In addition, many of these pathogens also secrete catalase-peroxidase, which breaks down H2O2 [S78–S82]."

Source: PLoS Pathog. 2012 Mar | Sleeping with the Enemy: How Intracellular Pathogens Cope with a Macrophage Lifestyle | Emily P. Thi, Ulrike Lambertz, and Neil E. Reiner | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3310772/

I had positive antibodies to Yersinia enterocolitica and Yersinia pseudotuberculosis in an LTT (lymphocyte transformation test) but a later western blot IgA and IgG test to YopH, YopM, YopB, LcrV, YopD, YopN, YopE all showed negative.

I don't know if I can trust the western blot test as the outer membrane proteins of the bacteria must be in the blood sample while in the LTT test the reaction of the lymphocytes to an antigen is tested.

Theriogenology. 2005 Apr 1;63(6):1667-81.
Gelatinases and serine proteinase inhibitors of seminal plasma and the reproductive tract of turkey (Meleagris gallopavo).
Kotłowska M, Kowalski R, Glogowski J, Jankowski J, Ciereszko A.

Conclusion: Amidase and anti-trypsin activities (expressed per gram of protein) differed for yellow and white seminal plasma.

Because the full article is not free I cannot see if the yellow seminal plasma had higher or lower Alpha-1-antitrypsin.
Alpha-1-antitrypsin inhibits the breakdown of tissue by enzymes, so could the higher albumin found in other studies be a sign of a lack of Alpha-1-antitrypsin?

Theriogenology. 1989 Sep;32(3):455-66.
Studies of chemical components of Angora goat seminal plasma.
Mendoza G, White IG, Chow P.

Conclusion: Colored semen was consistently produced by eight bucks, and in yellow, light yellow and white ejaculates, the seminal plasma riboflavin (mug/ml) concentrations were 5.38 +/- 2.89, 3.09 +/- 0.85 and 1.73 +/- 0.88, respectively.
This suggests that the color is due to riboflavin, which is probably produced by the vesicular glands since the concentration of riboflavin in the seminal plasma was correlated with fructose and citric acid levels.

See last study with same results.

Poult Sci. 1986 Mar;65(3):559-64.
Photoperiod, diet, and method of feeding on reproduction.
Dobrescu O.

Conclusion: All the groups of males given 8L:16D had an endemic yellow semen syndrome (YSS) characterized by a combination of an elevated seminal plasma protein concentration (an average of 12.85 g/100 ml), abnormal spermatozoa, and numerous macrophages.

In this case L stands for light and D for darkness, meaning 8 hours light and 16 hours darkness. I don't know how to interpret these results, lacking light will cause YSS? Or is it related to a lack of Vitamin D? I personally can exclude the latter cause.

Poult Sci. 1984 Oct;63(10):2084-6.
Detection and incidence of yellow turkey semen on commercial breeder farms.
Hess RA, Thurston RJ.

Conclusion: A low protein group (less than 8 mg/ml; 13.3% of the males) had 34 white, 2 slight yellow, and 0 yellow samples. A median protein group (10 mg/ml; 74.1%) had 175 white, 21 slight yellow, and 4 yellow. The high protein group (greater than 20 mg/ml; 12.5%) had 2 white, 14 slight yellow, and 18 yellow.

The more protein in the semen the more likely it was to be yellow(ish).

Biol Reprod. 1984 Sep;31(2):239-43.
Protein, cholesterol, acid phosphatase and aspartate aminotransaminase in the seminal plasma of turkeys (Meleagris gallopavo) producing normal white or abnormal yellow semen.
Hess RA, Thurston RJ.

Conclusion: Turkeys which produce yellow semen have abnormal ductuli efferentes' epithelial morphology, with blebbing of cytoplasmic material into the ductal lumen. This could possibly increase the activity or concentration of seminal plasma components.
(Ductuli efferentes connect the testicles with the epididymis)

Abnormal yellow seminal plasma, compared to normal white seminal plasma, had elevated levels of total protein and cholesterol and increased activities of acid phosphatase and aspartate aminotransaminase.

J Reprod Fertil. 1984 Jul;71(2):403-9.
Seminal plasma androgen-binding protein activity in turkeys with normal white or abnormal yellow semen.
Hess RA, Birrenkott GP Jr, Thurston RJ.

Conclusion: Yellow seminal plasma had a greater protein concentration and [3H]DHT binding activity averaging 32.5 +/- 7.93 pmol DHT/ml compared with 1.45 +/- 0.3 pmol DHT/ml for white seminal plasma.
We conclude that a seminal plasma androgen-binding protein is present in the domestic turkey, and in males with yellow semen syndrome androgen-binding activity is increased.

Poult Sci. 1983 Jan;62(1):169-74.
The influence of testosterone propionate on semen quality and testes morphology in the domestic turkey, Meleagris gallopavo.
Froman DP, Thurston RJ.

Conclusion: Neither corn oil nor testosterone propionate in corn oil caused YSS.

Poult Sci. 1982 Sep;61(9):1905-11.
Elevated seminal plasma protein: a characteristic of Yellow turkey semen.
Thurston RJ, Hess RA, Froman DP, Biellier HV.

Conclusion: Plasma from WS was white and averaged 1.84 +/- .07 g/100 ml protein, whereas YS seminal plasma was yellow with 7.03 +/- .5 g/100 ml protein.
Blood and seminal plasma protein concentrations were poorly correlated. That means if your blood albumin is normal it doesn't mean it is normal in semen.

Poult Sci. 1982 Mar;61(3):531-9.
Morphology of the epididymal region of turkeys producing abnormal yellow semen.
Hess RA, Thurston RJ, Biellier HV.

Conclusion: Male turkeys producing abnormal yellow-colored semen (YS) had hypertrophied epithelial cells in the ductuli efferentes. The cells were engorged with cytoplasmic, lipid-like (lipoid) droplets, a morphological abnormality found exclusively in this area of the epididymal region.
The testes, epididymal region, ductus deferens, and abdominal fat were relatively yellow compared to turkeys producing normal white semen (WS). Adipose tissue within the abdominal cavity and lining the ductus deferens was more abundant in the YS producers.
In addition to increased lipoid droplets, nonciliated cells of the ductuli epithelia contained larger and more numerous electron-dense lysosomal bodies than similar nonciliated cells in WS males. Resorption of morphologically normal and abnormal spermatozoa by the epithelia of the ductuli efferentes was prevalent in the YS males but was not observed in the WS turkeys.
The seminal fluids in the epididymal region of the YS males contained abnormal spermatids, cellular debris, and increased amounts of electron-dense proteinaceous material.

J Reprod Fertil. 1975 Nov;45(2):235-41.
Ultrastructural studies of semen abnormalities and Herpesvirus associated with cultured testicular cells from domestic turkeys.
Thurston RJ, Hess RA, Biellier HV, Adldinger HK, Solorzano RF.

Conclusion: Abnormal cells and macrophages found in white and yellow turkey semen were studied by electron microscopy. Yellow semen contained many abnormal cells, most of which were large and round or smaller and ellipsoidal. It was concluded that they were aberrant spermatids, with differentiation being more complete in the smaller cells.
Only a few cells of the smaller type were detected in normal white semen. Macrophages were occasionally seen in white semen but were numerous in yellow semen. Phagocytic vacuoles of these cells contained structural elements of spermatozoa and abnormal spermatids.
Virus particles were not detected in any of the seminal cells observed. Ultrastructure studies of cultured testicular cells obtained from several of the turkeys examined showed the presence of intranuclear Herpesvirus particles in germinal cells.
Macrophages from the testicular cultures seldom were seen with intranuclear Herpesvirus, although these cells commonly were found with Herpesvirus particles and cellular debris contained within phagocytic vacuoles.

Biochem J. 1960 Aug; 76(2): 301–306.
The yellow pigmentation of bull semen and its content of riboflavin, niacin, thiamine and related compounds
I. G. White and G. J. Lincoln

Conclusion: This study found a heriditary cause of yellow semen, which is probably caused by riboflavin which is produced in the seminal vesicles.
This is most likely unrelated to YSS and can be ruled out if you use a ultraviolet flashlight on a semen specimen as riboflavin produces a green fluorescence under ultraviolet light.

This is also used in "Riboflavin wash cycle validation"

What is the reason for the higher protein (mostly albumin) in YSS?

Is it from own tissue that is broken down? Is it a shedding of epithelial surface due to bacterial binding to albumin?

Source: J Biol Chem. 2011 Jan 28 | Binding of albumin promotes bacterial survival at the epithelial surface. | Egesten A, Frick IM, Mörgelin M, Olin AI, Björck L | https://www.ncbi.nlm.nih.gov/pubmed/21098039

I can personally rule out urine contamination in the semen as a cause of discoloration as there is a white streak which is about a quarter of the ejaculate and therefore must be the prostastic fluid.

In this graphic you can see the composition and release time of the several components:


Br J Clin Pharmacol. 2007 Apr; 63(4): 404–420.
A new method to estimate quantitatively seminal vesicle and prostate gland contributions to ejaculate
Themba T Ndovi, Teresa Parsons, Leena Choi, Brian Caffo, Charles Rohde, and Craig W Hendrix

Is it a hormonal issue? I definitely have low testosterone and I'm sure my semen was white before puberty, although my memory is not the best.

So whatever the cause is it must be related to the seminal vesicles. As this is the place where the fluid is enriched with fructose for spermatozoa energy supply, this could also be a supply for bacteria.

Could a low testosterone level cause increased level of lipofuscin (a yellow-brown pigment) in the seminal vesicles?

Source: Reproduction. 2004 Mar | Age-induced apoptosis in the male genital tract of the mouse. | Jara M, Carballada R, Esponda P. | https://www.ncbi.nlm.nih.gov/pubmed/15016955

Methylene Blue as a solution for this?

Source: Z Alternsforsch. 1981 | Morphological studies of the pigment present in the seminal vesicles of orchidectomized hamsters, and the preventive action of vitamin E and methylene blue. | Granados H, Beregi E. | https://www.ncbi.nlm.nih.gov/pubmed/7222753