Can hyperthyroidism lead to polycythaemia vera?
Q: I am a 24-year-old male. I have hyperthyroid for the last seven years and I have been taking one tablet of Thyrox 100 for the same. But for the last three months, my uric acid has increased. I have been taking Thyrox 100 for three months now and the doctor has asked me to continue it for another 6-7 months. Recently, during one of the CBC tests, it was found that my haemoglobin is 17.9 g/dl, haematocrit is 53.4%, RBC is 6.31 x 10^12/l, WBC is 7.8 x 10^9/l and platelets are 429 x 10^9/l. Even after eight months, the reports indicate the same status in terms of increased RBC, haematocrit and haemoglobin. Kindly advise how serious is the disease. The doctor has asked me to donate blood to reduce the haematocrit levels. Can a person suffering from hyperthyroidism donate blood? Does my hyperthyroidism have anything to do with the problems in my haemoglobin and RBC? Is there a possibility of polycythaemia vera and cancer? What are the precautions that I need to take in future?
A:The number of red cells normally present varies according to a person's age and sex. Men have higher results than women do and newborn babies often have higher values than adults. The presence of an elevated red cell count is called erythrocytosis or a polycythaemia. This increase in red cells may show in a blood test result as an increase in red cell number, or as a rise in haemoglobin, or packed cell volume. Red blood cell production is governed by a hormone called erythropoietin that is secreted by the kidney. Erythrocytosis is not a disease but is usually part of some other problem. There are no specific symptoms or physical signs although the underlying disease may cause the patient to seek medical help. Many times, the high haematocrit is noticed when a person has a blood count done as part of an exam for an unrelated complaint. The normal haemoglobin value in an adult male can range up to 18 g/dl. It can be raised due to many reasons and these causes may be subdivided into whether there is a true or absolute erythrocytosis (polycythaemia) due to an increase in red cells or an apparent erythrocytosis when the red cells are not increased but are instead more concentrated. The secondary increase can be due to dehydration, diuretic drugs, burns, stress, or high blood pressure. True polycythaemia may be primary and is then called polycythaemia vera, a myeloproliferative disorder in which the RBC count increases without being stimulated by the red blood cell stimulating hormone erythropoietin. Secondary polycythaemia is due to an increase in RBC counts following an increase in the hormone erythropoietin. This hormone increase is in response to low blood oxygen, caused by heart disease or high altitude; continual exposure to carbon monoxide (heavy smoking); chronic lung disease, congenital (hereditary) disorders producing an abnormal haemoglobin or an overproduction of EPO; and diseases such as kidney disease. Symptoms of polycythaemia include easy bruisability, purpuric spots on skin, blood in the stool, blood clots, painful redness of the skin and warmth in parts of the limbs, blackening of the fingers or toes (necrosis), fever, heat tolerance, weight loss, and itching. If an underlying problem is found, it can usually be corrected, and the erythrocytosis should disappear. If there is not a correctable problem, then further management depends on how high the haematocrit is. If the haematocrit is just a little above normal, perhaps nothing needs to be done. However, if the haematocrit gets too high (above 60 per cent), it thickens the blood, causing circulatory difficulties that may result in strokes and heart problems. To avoid these problems, the patient can have phlebotomies (blood-letting) to reduce the haematocrit. One unit of blood can be removed every few days or once a week until the haematocrit is down and then done at intervals of time to keep it down. Phlebotomy is like donating blood though the blood cannot be used because of the underlying problem. To the best of my knowledge there is no relation between erythrocytosis and hyperthyroidism. You need to get the following tests done: A complete blood count (as both the total white cell count and platelets are raised in polycythaemia); iron studies; vitamin B12 levels (usually raised); bone marrow examination (to exclude panmyelosis); cytogenetic studies; arterial oxygen saturation and erythropoietin levels. Please consult a haematologist who can discuss all this with you and advise.