Chronic Kidney Disease Is Common in Thyroid Dysfunction
Another comorbidity, chronic kidney disease (CKD), commonly occurs in patients with thyroid dysfunction and T2D.4 While overt thyroid dysfunction is not as frequent as subclinical thyroid disorder, it can still manifest in patients with T2D.4 To assess the effect of subclinical hypothyroidism on renal function, measured by estimated glomerular filtration rate (eGFR), researchers conducted a retrospective study of 5936 patients with T2D who visited the Nanjing First Hospital in Jiangsu, China.4
Compared with euthyroid participants, patients with subclinical hypothyroidism had a lower eGFR (82.7 vs 90.5 mL/min/1.73 m2, respectively; P <.05), higher urine albumin excretion (114 vs 88 mg/24 h, respectively; P <.05), and higher incidence of CKD (16.0% vs 10.1%, respectively; P <.05).
In patients with normal TSH levels, individuals with a lower TSH level — between 0.55 and 3.0 μIU/mL — had a higher eGFR (91.4 mL/min/1.73 m2) and a lower prevalence of CKD (9.5%) than patients with higher TSH between 3.01 and 4.78 μIU/mL (eGFR, 85.6 mL/min/1.73 m2; CKD prevalence, 13.1%; P <.01 for both).4
“Subclinical [thyroid dysfunction] is less studied, and the best approach depends on the overall condition of the affected patients, especially the ones with subclinical hypothyroidism,” noted endocrinologist Dongmei Li, MD, from the Nanjing First Hospital, Nanjing Medical University, in Jiangsu, China. “The common suggestion is to keep on observation when TSH is not higher than 5 μIU/mL, add a low dose of [levothyroxine] when TSH is higher than 5 μIU/mL, and carefully monitor.”
Endocrine Disruptors: Another Layer of the Association Between Diabetes and Thyroid Dysfunction
Complicating matters are the chemicals in the environment, collectively termed endocrine disruptors, which can cause obesity.5 Even household dust was implicated in spurring the activity of triglyceride accumulation, which in turn led to greater body mass index, as well as higher serum TSH levels in patients who were exposed to higher levels of dust.5
As for why clinicians may not fully appreciate the link between obesity, diabetes, and thyroid dysfunction, postdoctoral research fellow Christopher D. Kassotis, PhD, from Duke University’s Nicholas School of the Environment in Durham, North Carolina, offered: “There is a growing movement to make clinicians more aware of these issues and our understanding of the influence of various chemicals on health impacts, but it is not yet a standard component of most medical training programs. Groups like the Endocrine Society have vastly helped this process, but we still have a long way to go in connecting endocrine health researchers to clinicians.”
Summary & Clinical Applicability
Diabetes and thyroid dysfunction are the most frequently occurring endocrine disorders. Clinicians should closely monitor patients with either disorder and consider how treatment of one may exacerbate the other due to drug-drug interactions.
Limitations & Disclosures
1. Biondi B, Kahaly GJ, Robertson RP. Thyroid dysfunction and diabetes mellitus: two closely associated disorders [published online January 14, 2019]. Endocr Rev. doi:10.1210/er.2018-00163
2. Jonklaas J, Razvi S. Reference intervals in the diagnosis of thyroid dysfunction: treating patients not numbers [published online February 20, 2019]. Lancet Diabetes Endocrinol. doi:10.1016/S2213-8587(18)30371-1
3. Barmpari ME, Kokkorou M, Micheli A, et al. Thyroid dysfunction among Greek patients with type 1 and type 2 diabetes mellitus as a disregarded comorbidity. J Diabetes Res. 2017;2017:6505814.
4. Zhang Y, Wang Y, Tao XJ, et al. Relationship between thyroid function and kidney function in patients with type 2 diabetes. Int J Endocrinol. 2018;2018:1871530.
5. Kassotis CD, Stapleton HM. Endocrine-mediated mechanisms of metabolic disruption and new approaches to examine the public health threat. Front Endocrinol (Lausanne). 2019;10:39.