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Problems affecting one part of the body can impact many other organs and tissues.
Hypothyroidism is one of those conditions whose consequences are felt throughout the body as it can cause problems with heart function, hearing, and many others.
Can hypothyroidism affect kidneys?
That’s the question we’re going to examine throughout this article.
Does hypothyroidism affect kidneys?
Although both hypothyroidism and kidney problems are common, more studies are needed to evaluate their relationship. However, current evidence confirms that hypothyroidism can indeed affect kidney function.
For example, the September 2016 issue of Kidney Research and Clinical Practice published a study whose primary objective was to evaluate the prevalence of hypothyroidism among patients with chronic kidney disease (CKD). For the purpose of the study, scientists analyzed data from the CKD patients in one hospital in northern India. A total of 1863 patients were evaluated, of whom 358 underwent biochemical analysis for hypothyroidism. Of these, 143 had subclinical biochemical hypothyroidism while 59 had overt hypothyroidism. Scientists found that patients with hypothyroidism had significantly lower levels of serum calcium and albumin compared to their non-hypothyroid counterparts. They concluded the study saying that there is growing evidence of the increased prevalence of hypothyroidism among CKD patients. That’s why there is a need to screen patients with kidney problems for hypothyroidism and levels of calcium and albumin[i].
This wasn’t the only research that confirmed the relationship between hypothyroidism and kidney disease.
A different study, published in the Current Opinion in Endocrinology, Diabetes, and Obesity also dived into the same subject. The primary objective of the review was to examine potential mechanistic links between thyroid and kidney disease. Their findings showed that there is a higher prevalence of hypothyroidism with increasing severity of kidney dysfunction. Furthermore, various thyroid function test abnormalities are observed in patients with CKD due to changes in synthesis, metabolism, and regulation of thyroid hormones. Scientists call for more rigorous studies to evaluate this relationship and determine the impact of thyroid hormone replacement on the progression of kidney disease, cardiovascular disease, and mortality[ii].
Another article from the May 2018 issue of the Mayo Clinic Proceedings discussed the unwanted synergy between thyroid problems and kidney disease. They report that end-stage renal disease is indicated by exceedingly high rates of cardiovascular disease and mortality, but both hypo- and hyperthyroidism with further increases in mortality among these patients. Scientists also report that both hypothyroidism and hyperthyroidism conditions increased mortality in patients with stage 3 of CKD by 17% to 27%. Interestingly, the risk was higher in patients younger than 60 years of age compared to their older counterparts. Once again, the scientists stressed the importance of screening patients with CKD for thyroid hormone levels both to understand the magnitude of the problem and to allow the prospective evaluation[iii].
Why does hypothyroidism affect kidneys?
As seen above, the relationship between hypothyroidism and kidney disease is evident. That being said, underlying mechanisms that connect the two are still largely unknown. It is important to carry out more studies on this subject in order to learn how and why hypothyroidism affects kidneys.
What we do know, based on the studies mentioned above, is that TSH level is often elevated in patients with CKD in response to thyrotropin from pituitary as a result of the uremic effect. Additionally, poor glycosylation compromises bioactivity of TSH and impairs its circadian rhythm. Glycosylation occurs when sugar molecules or glucose float around in the blood and attach to protein molecules, thus diminishing their effectiveness. One of the contributing factors in the rise of hypothyroidism among CKD patients is chronic metabolic acidosis, which occurs when the body produces too much acid.
Mariani et al. found that hypothyroidism adversely affects kidney size and structure in both development and adulthood. The impact of thyroid hormone is in part due to direct renal actions and in part is mediated by cardiovascular and systemic hemodynamic effects that influence the function of the kidneys[iv]. Hypothyroidism can reduce kidney-to-body weight ratio and affect the function of kidneys through various mechanisms, which include:
- Increased cardiac output
- Altered intra-renal hemodynamic i.e., intra-renal vasoconstriction (narrowed vessels) caused by decreased vasodilator synthesis and activity
- Reduced production and activity of rennin-angiotensin-aldosterone which is a hormone system that regulates blood pressure and fluid and electrolyte balance, systemic vascular resistance
- Enhanced tubuloglomerular feedback due to alterations in chloride channel and expression. Tubuloglomerular feedback is defined as a feedback system inside the kidneys, and it’s important for their function
Moreover, hypothyroidism can reduce single nephron glomerular filtration rate, renal plasma flow, and glomerular transcapillary pressure, all of which impair the function of your kidneys. Single nephron glomerular rate assesses the function of individual nephrons, which are functional units of kidneys. The sheer fact that hypothyroidism could impair the filtration rate of nephrons explains the negative impact of this condition on kidney function as well as its potential to contribute to and aggravate CKD.
What’s more, severe hypothyroidism leads to creatinine elevations, which signify impaired kidney function and kidney disease. Creatinine is the waste product of creatine which the muscles use to make energy.
The same way hypothyroidism jeopardizes kidney function and contributes to CKD, kidney problems can lead to impaired thyroid function as well. Disturbed kidney excretion can lead to iodine retention, which is a major mechanism of action behind the relationship of renal diseases with hypo- and hyperthyroidism. At the same time, patients with CKD may frequently have metabolic acidosis, which has been shown to result in alterations of functional thyroid test (low T4 and T3, elevated TSH levels).
Despite the fact that science has confirmed that hypothyroidism and kidney disease have a two-way relationship as one can lead or contribute to the other, little is known about all mechanisms that connect them. One potential indirect mechanism of action could be high cholesterol.
The body needs thyroid hormones to make cholesterol and to eliminate cholesterol it doesn’t need anymore. That being said, hypothyroidism impairs the breakdown and removal of LDL or bad cholesterol, which then accumulates in the blood. In fact, high cholesterol is one of the hallmark symptoms of hypothyroidism.
What many people don’t know is that high cholesterol can negatively affect kidneys too. Not only does cholesterol contribute to heart disease risk, but it also clogs the renal arteries and cuts off blood flow to the kidneys, thus weakening kidney function[v]. Therefore, hypothyroidism can negatively affect kidneys by increasing cholesterol levels. This is why it’s important to be proactive and manage symptoms you experience adequately by following doctor’s orders and recommendations. Through proper management of symptoms such as high cholesterol, you can protect your kidneys.
Weight gain is one of the biggest telltale signs of hypothyroidism. This condition can make a person gain weight, which can only aggravate other symptoms.
Thyroid hormones are crucial for metabolism. When their production decreases, the metabolism slows down, which leads to weight gain. Excess weight can put your health in danger, including kidney function. Studies show that overweight and obesity can increase the risk of kidney disease[vi].
Overweight and obesity force the kidneys to work harder and filter wastes above the normal level. Over time, this increased work output can put you in jeopardy and elevate the risk of kidney disease. This is yet another indirect manner through which hypothyroidism can contribute not only to cardiovascular diseases and diabetes but poor kidney function as well.
Am I at risk of kidney disease?
Everyone can develop kidney problems, but some people are at a higher risk than others. Learning risk factors can make it easier for you to prevent such problems and protect your kidneys.
Let’s take a look at some of the most common risk factors that lead to kidney problems:
- Diabetes – One of the most common causes of kidney disease is that too much insulin that stays in the blood can affect renal function. It’s also worth mentioning that hypothyroidism can also contribute to or worsen diabetes as well.
- High blood pressure – Hypertension means the heart is working too hard to pump the blood, which can damage tiny vessels in the kidneys.
- Family history of kidney disease – Like many other health problems those affecting kidneys are also more likely to develop in persons who have family members with renal disease.
- Ethnicity – African-Americans, Hispanics, Native Americans, and Asians are at a higher risk of developing hypertension and diabetes which makes them also more likely to suffer from kidney problems
- Age – The older you are the risk of kidney problems increases. People who are older than 60 have a higher risk of developing kidney problems than the younger population.
- Obesity – As mentioned above, excess weight makes kidneys work harder which can lead to impaired function in the long run.
- Smoking – This unhealthy habit increases the risk of many health problems besides lung cancer. Kidney disease is one of those problems. Smoking narrows down blood vessels which prevent kidneys from getting the blood they need for proper function
- History of acute kidney injury – Acute kidney injury occurs when kidneys stop working suddenly for a short period of time. People who have experienced this problem are also more likely to develop kidney disease.
How to protect kidneys
Kidneys work hard to keep you strong and healthy. However, they’re sensitive, and we need to take care of them properly. Fortunately, simple lifestyle modifications can help us protect kidneys from damage. If you have hypothyroidism, feel free to consult your doctor and ask for necessary tests to examine kidney function. The same goes for persons with kidney disease; doctors should screen your thyroid.
Persons with hypothyroidism can protect their kidneys by adhering to doctor-recommended treatment. Managing symptoms of hypothyroidism could also tackle high cholesterol and hypertension. Try adopting some healthier lifestyle habits such as:
- Drink plenty of water
- Ditch unhealthy foods and opt for healthy nutritious alternatives to manage weight
- Exercise regularly
- Reduce salt intake
- Quit smoking
- Avoid alcohol
- Monitor sugar intake
- Monitor your blood pressure
- Limit intake of NSAIDs because they put a strain on your kidneys
Kidneys keep us alive, and we need to take care of them properly.
Doctors should evaluate kidney function of persons with hypothyroidism and vice versa.
At the same time, if you have hypothyroidism, you may want to adopt healthier lifestyle habits to keep your kidneys strong and healthy.
While many studies have confirmed the relationship between hypothyroidism and kidney disease, underlying mechanisms are still largely unknown, and further research is needed to elucidate them.
[i] Chandra A. (2016). Prevalence of hypothyroidism in patients with chronic kidney disease: a cross-sectional study from North India. Kidney research and clinical practice, 35(3), 165–168. doi:10.1016/j.krcp.2016.06.003. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5025463/
[ii] Rhee C. M. (2016). The interaction between thyroid and kidney disease: an overview of the evidence. Current opinion in endocrinology, diabetes, and obesity, 23(5), 407–415. doi:10.1097/MED.0000000000000275. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5094898/
[iii] Stan MN, Drake MT. (2018). Failing kidneys and thyroid dysfunction – an undesirable synergy. Mayo Clinic Proceedings, 93(5), 555-557. Doi: 10.1016/j.mayocp.2018.03.027. Retrieved from: https://www.mayoclinicproceedings.org/article/S0025-6196(18)30237-4/fulltext
[iv] Mariani LH, Berns JS. (2012). The renal manifestations of thyroid disease. Journal of American Society of Nephrology, 23(1), 22-26. Doi: 10.1681/ASN.2010070766. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/22021708/
[v] cholesterol and chronic kidney disease, DaVita. Retrieved from: https://www.davita.com/education/kidney-disease/risk-factors/cholesterol-and-chronic-kidney-disease
[vi] Lai YJ, Hu HY, Lee YL, (2017). Association between obesity and risk of chronic kidney disease: a nationwide cohort study in Taiwan. Nutrition, Metabolism, and Cardiovascular Diseases, 27(11):1008-1014. Doi: 10.1016/j.numecd.2017.08.006. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/28986076