Selenium nails

An endemic disease in China, characterized by loss of hair and nails, skin lesions, and abnormalities of the nervous system, including some paralysis and hemiplegia, was attributed to chronic selenium poisoning. The daily intake for six affected individuals averaged 5.0mg versus 0.1 mg for people from an unaffected area. Changing the diet led to... 

Toxicity and health effects Selenium causes hair and nail loss, discoloration and decay of the teeth, and CNS disturbances, including pain and anesthesia of the extremities. Inhalation of hydrogen selenide causes pulmonary edema. The dusts of selenium produce respiratory tract irritation, while the fumes of selenium dioxide produce metal fume fever. Dermal exposure and ingestion of selenium oxychloride cause skin burns, corrosive injury to the gastrointestinal tract, stupor, respiratory depression, and refractory hypotension. Ingestion of selenious acid causes corrosive injury to the gastrointestinal tract, stupor, respiratory depression, and refractory hypotension... 

Gladyshev, V. N., Khangulov, S. V., Axley, M. J., and Stadtman, T. C., 1994, Coordination of selenium to molybdenum in formate dehydrogenase H from Escherichia coli, Proc. Nail. Acad. Set (USA) 91 7708ii7711. 

Human selenosis has been reported from the Enshi district, Hubei Province, China. Between 1923 and 1988,477 cases of human selenosis were reported, 338 resulting in hair and nail loss and disorders of the nervous system. In one small village, the population was evacuated after 19 of 23 people suffered nail and hair loss, and all the livestock had died from selenium poisoning. Cases of selenosis in pigs reached a peak between 1979 and 1987, when 280 out of 2,238 pigs were affected in one village. 

Fungal infections superficial dermatophyte or Candida infections purely involving the skin can be treated with a topical imidazole (e.g. clotrimazole, miconazole). Pityriasis versicolor, a yeast infection, primarily involves the trunk m young adults it responds poorly to imidazoles but topical terbinafine or selenium sulphide preparations are effective severe infection may require systemic itraconazole. Invasion of hair or nails by a dermatophyte or a deep mycosis requires systemic therapy terbinafine is the most effective drug. Terbinafine and griseo-fulvin are ineffective against yeasts, for which itraconazole is an alternative. Itraconazole can be used in weekly pulses each month for 3-4 months it is less effective against dermatophytes than terbinafine. 

In summary, there are many possible markers for selenium status. In practice, measurement of plasma selenium or GSHPx provides a good estimate of status and in particular the adequacy of recent intake, provided they are interpreted in the knowledge of changes in the APR. For a better index of long-term intake, platelet, red cell, or neutropinl GSHPx, or hair or nail selenium can also be measured. 

The reference interval for selenium in whole blood, plasma or serum, hair, and nails should be established locally, since these indices are affected by dietary selenium intake. Plasma selenium adult values lie in the interval 63 to 160pg/L (0.8 to 2.0pmol/L). Values of less than 40 pg Se per L (0.5pmoI/L) indicate probable selenium depletion. 

Harrison I, Littlejohn D, FeU GS. Determination of selenium in human hair and nail by electrothermal atomic absorption spectrometry. J of Analytical Atomic Spectroscopy 1995 10 215-9. 

Selenium Muscle weakness and pain, cardiomyopathy Nausea, vomiting, hair and nail loss, tooth decay, skin lesions, irritability, fatigue, peripheral neuropathy Decreased malignancy, liver failure, pregnancy Increased reticuloendothelial neoplasia... 

Selenium can be measured in the blood, urine, and fingernails or toenails of exposed individuals. However, since selenium is an essential nutrient normally present in foods, low levels of selenium are normally found in body tissues and urine. Tests for selenium are most useful for people who have recently been exposed to high levels. Samples of blood, urine, or nails can be properly collected in a physician s office and sent to a laboratory that has the special equipment needed to measure selenium. Urine can be used to determine short-term exposure. Because red blood cells last about 120 days before they are replaced by newly made red blood cells, the presence of selenium in red blood cells can show whether a person was exposed to selenium during the 120 days before testing, but not if exposed more than 120 days before testing. Toenail clippings can be used to determine longer term exposure. 

Selenosis. Following chronic oral exposure to excessive amounts of the organic selenium compounds found in food, the two principal clinical conditions observed in humans are dermal and neurological effects, as described most completely in the epidemiological study of endemic selenosis in the People s Republic of China. The dermal manifestations of selenosis include loss of hair, deformation and loss of nails, and discoloration and excessive decay of teeth, while neurological effects include numbness, paralysis, and occasional hemiplegia. 

No evidence of nail disease was observed in a population living on selenium-rich ranches in the western United States (Longnecker et al. 1991). Doses of selenium were calculated to be between 0.001 and 0.01 mg/kg/day, corresponding to a maximum intake of 0.724 mg/day. Whole blood selenium concentrations were 0.18-0.67 mg/kg. Although these values for the United States are consistent with studies of the Chinese population, only one or a few individuals ingested the highest doses. 

Five individuals from the high selenium region of China described by Yang et al. (1989a) who had been diagnosed with overt signs of selenosis (hair loss and nail sloughing) in 1986 were reexamined in 1992... 

Yang and Zhou 1994). The results of this examination showed that these individuals had recovered from selenosis (overt symptoms of nail sloughing were absent) and that the average selenium concentrations in their blood had fallen from 1,346 to 968 pg/L. The corresponding dietary intakes of selenium were 1,270 and 819 pg/day. This study has been used to establish a LOAEL of 0.023 mg selenium/kg/day and a NOAEL of 0.015 mg selenium/kg/day. Based on the occurrence of these dermal effects, a chronic oral MRL of 0.005 mg selenium/kg/day has been derived from the NOAEL, as described in the footnote in Table 3-2. This MRL is 5 times greater than the recommended dietary allowance (RDA) for selenium of 0.001 mg/kg/day. 

Selenium accumulates in many organ systems in the body in general, the highest concentrations are found in the liver and kidney (Table 3-6). Selenium concentrations in tissues do not seem to be correlated with effects. Tissue concentrations were highest in pigs fed D,L-selenomethionine, while a similar dose of selenium (form not stated) given as A. bisulcatus was a more potent neurotoxin. Blood, hair, and nails also contain selenium, and selenium has been found in human milk (Table 3-7). In addition, selenium is subject to placental transfer. 

Little is known about the specific biochemical mechanism(s) by which selenium and selenium compounds exert their acute toxic effects. Long-term effects on the hair, skin, nails, liver, and nervous system are also well documented, and a general theory has been developed to explain the toxicity of exposure to excess selenium, as discussed below. Generally, water-soluble forms are more easily absorbed and are generally of greater acute toxicity. Mechanisms of absorption and distribution for dermal and pulmonary uptake are unknown and subject to speculation, but an active transport mechanism for selenomethionine absorption in the intestine has been described (Spencer and Blau 1962). The mechanisms by which selenium exerts positive effects as a component of glutathione peroxidase, thioredoxin reductase, and the iodothyronine 5 -deiodinases are better understood, but the roles of other selenium-containing proteins in mammalian metabolism have not been clarified. 

Specific biomarkers of selenium effects were not found. Garlic breath is a marker of over-exposure to selenium compounds. However, as other metals that are methylated (e.g., arsenic) also result in garlic odor of the breath, this effect is not a unique marker of selenium over-exposure. Hair and nail effects may be the most frequent effects of overexposure to selenium. Hair becomes dry and brittle and breaks... 

Exposure. Selenium exposure can be correlated with concentrations detected in human blood, blood components, urine, hair, and nails. Selenium concentrations found in these biomarkers in the general population can be found in Table 3-7. However, these markers vary greatly among different populations (Longnecker et al. 1991). Levels of plasma, erythrocyte and platelet GSH-Px activity, as well as selenoprotein P may serve as better markers of selenium deficiency than selenium concentrations. 

Effect. Perhaps the earliest and most frequent symptoms of selenosis in humans are dry and brittle hair that breaks off, and brittle nails with white spots or streaks. Although these effects may not be specific to selenium, determination of selenium status may be useful if they are observed in a subject. Additional, biomarkers of negative effects that could be detected before clinical signs of selenium toxicity could be helpful in preventing selenium poisoning. 

Rogers MA, Thomas DB, Davis S, et al. 1991. A case control study of oral cancer and pre-diagnostic concentrations of selenium and zinc in nail tissue. Int J Cancer 48(2) 182-188. 

Salbe AD, Levander OA. 1990b. Effect of various dietary factors on the deposition of selenium in the hair and nails of rats. J Nutr 120(2) 200-206. 

Van Noord PAH, Maas MJ, De Bruin M. 1992. Nail keratin as monitor-tissue for selenium exposure. Trace Elements in Medicine 9(4) 203-208. 

---