Kidney Failure in the Elderly Due to Hypothyroidism: a Case Report

CONTEXT: Hypothyroidism is more prevalent in the elderly and its symptoms can be confused with other changes due to aging. Doctors caring for the elderly need to be attentive to this diagnostic possibility. This case report case is notable not only because it presents a rare complication of hypothyroidism (kidney failure), but also because patients with chronic kidney failure of any etiol-ogy may suffer increased renal dysfunction as a result. CASE REPORT: This was a 66-year-old male outpatient with a history of generalized edema over the preceding eight years, with periods of worsening, that was intractable to treatment with diuretics. Physical examination revealed bradycardia (heart rate: 52 bpm), pallor, dry and infi ltrated skin, macroglossia, edema in the lower limbs and a palpable thyroid with hard consistency. Laboratory tests showed: creatinine 3.9 mg/dl; urea 95 mg/dl; potassium 6.0 mEq/l; thyroid-stimulating hormone > 100 mUI/ ml; triiodothyronine 0.01 ng/dl; free thyroxin 0.01 ng/dl; antithyroglobulin 31 IU/ml (normal values: < 40 IU/ml); antithyroperoxidase 85 IU/ml (normal values: < 15 IU/ml); creatinine clearance 30 ml/min/1.73 m 2 ; and proteinuria 122 mg/24 h. After fi ve months of treatment with thyroxin (100 mcg/day), the patient returned without any symptoms and presented the following test results: urea 48 mg/dl; creatinine 1.4 mg/dl; creatinine clearance 67 ml/min/1.73 m 2 ; potassium 4.2 mEq/l; thyroid-stimulating hormone: 20.85 mUI/ml; free thyroxin: 0.71 ng/dl. Hypothyroidism alone can cause renal impairment or worsen renal function in preexist-ing illnesses. Its treatment can stabilize the clinical condition, or possibly improve it. INTRODUCTION Hypothyroidism has high prevalence among the elderly. Among individuals over 60 years old, it affects 10% of women and 2% of men.


INTRODUCTION
Hypothyroidism has high prevalence among the elderly.Among individuals over 60 years old, it affects 10% of women and 2% of men. 1 The primary form of hypothyroidism can be caused by surgery or by treatment with radioactive iodine.The idiopathic primary form of this illness is associated with circulating antithyroid antibodies, 2,3 which can block the thyroid-stimulating hormone receptor.In some cases, drugs such as amiodarone 4 and lithium 1 can act like these antibodies.Hypothyroidism can coexist with other autoimmune diseases like diabetes mellitus, Addison's disease, pernicious anemia, vitiligo and chronic hepatitis. 5,6It may also be associated with kidney abnormalities. 7ymptoms such as cold intolerance, weight gain, dry skin, intestinal constipation or mental and physical slowness can be confused with the normal signs or effects of aging. 1 Illnesses like depression and dementia can be caused or worsened by hypothyroidism.It may also be responsible for carpal tunnel syndrome, walking problems (muscle weakness), slower muscle reactions, ataxia and neuropathy.In elderly people with multiple illnesses, the use of different kinds of medication and their side effects may mimic or mask the symptoms of hypothyroidism.The laboratory test abnormalities resulting from hypothyroidism are quite varied: macrocytosis with or without anemia, elevated cholesterol and plasma triglycerides, inexplicable hyponatremia and elevation of the enzymes creatine phosphokinase and lactate dehydrogenase. 1 Some studies have suggested that hypothyroidism should be evaluated in patients with kidney abnormalities. 8,9This hormonal defi ciency can lead to kidney diseases: since thyroid hormones are responsible for the growth and development of the kidneys, they have an infl uence on substance transportation through the membrane and modify the electrolytic metabolism.This leads to deficits of renal function, associated with reductions in the cardiac output. 10,11It can also cause glomerulopathy (nephritic and/ or nephrotic syndrome) and occur in diverse forms of chronic kidney disease, including in hemodialysis patients, thereby worsen ing the prognosis. 10Most kidney abnormalities (structural, metabolic and morphological) caused by hypothyroidism can be reverted after supplementation with thyroxin. 11ere, we describe the case of a patient attended at the geriatric outpatient clinic of Hospital do Servidor Público Estadual, in São Paulo, who was diagnosed as presenting renal dysfunction associated with hypothyroidism.The importance of this report lies in the high prevalence of this association, since primary hypothyroidism can occur in 9.5% of the patients with chronic renal disease, compared with a prevalence of 0.6 to 1.1% in the general population.Hence, primary hypothyroidism is often underdiagnosed. 12,13Moreover, the kidney disease in such patients is potentially reversible when treated appropriately.

CASE REPORT
This was a 66-year-old male outpatient with a history of generalized edema over the preceding eight years, with periods of worsening, who was unresponsive to diuretics.Physical examination revealed bradycardia (heart rate 52 bpm), pallor, dry and infi ltrated skin, macroglossia, edema in the lower limbs and an enlarged thyroid with hard consistency.
After five months of treatment with thyroxin 100 mcg/day, the patient returned to the outpatient clinic without any symptoms.He presented the following test results: urea 48 mg/dl, serum creatinine 1.4 mg/dl, creatinine clearance 67 ml/min/1.73m 2 , potassium 4.2 mEq/l, thyroid-stimulating hormone 20.85 m IU/ml and free thyroxin 0.7 ng/dl.

DISCUSSION
Hypothyroidism in older patients is most often primary.It is caused by autoimmune disorders, previous thyroidectomy or application of treatment for hyperthyroidism.Organ-specific autoimmunity increases with advancing age and, hence, Hashimoto thyroiditis remains the main cause of thyroid failure in older patients. 14he different causes of hypothyroidism result in similar symptoms like bradycardia, hypertension, delayed tendinous reflex actions, cramps, increased muscle mass, weakness, dry and coarse skin, non-depressive edema, intol-erance to cold and increased body weight. 14In most patients, the slow and gradual beginning of the illness may make diagnosis difficult.This was exactly how it occurred in the case of our patient, who was referred to us with history of long-term edema that was resistant to diuretics.Previous investigations had not led to any diagnosis of hypothyroidism.
In this case, the patient presented a very high level of thyroid-stimulating hormone and reduced levels of triiodothyronine and free thyroxin, which confirmed the previous diagnosis.The finding of antithyroid antibodies was compatible with Hashimoto thyroiditis. 14ypothyroidism is often associated with kidney diseases. 15These renal abnormalities occur because the deficiency of thyroid hormones reduces the cardiac output.Consequently, this deficiency reduces the renal blood flow and, finally, the glomerular filtration rate. 11,16The result from this is an elevation in the serum levels of creatinine and a reduction in its clearance.There may also be slight proteinuria, secondary to increased capillary transudation of proteins. 8In serious cases, there may be acute kidney failure due to rhabdomyolysis.In our case, this was ruled out, since the level of creatine phosphokinase was normal.Likewise, hypothyroidism can also explain the deterioration in renal function among patients with chronic renal illness.
Studies that have commented on this association have suggested that thyroid hor-mone assays should be performed in the cases of patients whose renal function is quickly worsening.In addition, a study on patients with chronic renal failure who underwent continual outpatient peritoneal dialysis treatment showed a greater association with thyroid nodules and hypothyroidism than among control group patients.Consequently, this suggests that the presence of thyroid nodules and assays on thyroid hormone levels should be routinely investigated among chronic kidney failure patients. 15fter a five-month period, we observed that our patient presented renal function recovery, as shown by clinical and laboratory parameters.This finding is in line with descriptions in the literature.It needs to be noted that the patient did not have any chronic illness that could have led to kidney failure and he was not using any nephrotoxic medication.

CONCLUSION
Hypothyroidism must be suspected either as a cause of kidney disease or as a factor in the worsening of renal dysfunction in patients with chronic kidney failure.Treatment with thyroid hormones enhances renal function, thus improving the glomerular filtration rate.Assaying of thyroid-stimulating hormone levels should be considered as a screening test for patients with renal abnormalities.