Thyroid hormone abnormalities at diagnosis of insulin-dependent diabetes mellitus in children

Italian Association of Clinical Endocrinologists (AME) & Italian Association of Clinical Diabetologists (AMD) Position Statement : Diabetes mellitus and thyroid disorders: recommendations for clinical practice

Thyroid disease and diabetes mellitus, the most common disorders in endocrine practice, are not infrequently associated in the same subject. An altered thyroid function may affect glucose tolerance and worsen metabolic control in patients with diabetes. Thyrotoxicosis increases the risk of hyperglycemic emergencies, while a clinically relevant hypothyroidism may have a detrimental effect on glycemic control in diabetic patients. The association of alterations in thyroid function with diabetes mellitus may adversely affect the risk of cardiovascular and microvascular complications resulting from diabetes. Moreover, the treatments used for both diabetes and thyroid disease, respectively, can impact one other. Finally, multinodular goiter, but not thyroid carcinoma, was shown to be more prevalent in type 2 diabetes mellitus. Aim of the present Position Statement is to focus on the evidence concerning the association of thyroid disease and diabetes mellitus and to provide some practical suggestions for an updated clinical management.

Relationships between thyroid function and autoimmunity with metabolic derangement at the onset of type 1 diabetes: a cross-sectional and longitudinal study

BACKGROUND

Type 1 diabetes (T1DM) is an autoimmune disease often associated with thyroid abnormalities.

PURPOSE

We investigated the correlation between thyroid function and metabolic derangement at onset and the influence of autoimmunity on thyroid function at onset and subsequently.

METHODS

We evaluated 152 patients diagnosed with T1DM between 2000 and 2012 at onset and during a mean follow-up of 5.45 ± 2.8 years. Thyroid function at onset was correlated with metabolic derangement (degree of acidosis, metabolic control and adrenal function) and compared with that of 78 healthy children. Follow-up consisted of regular evaluation of thyroid function and autoimmunity.

RESULTS

Thyroid hormonal pattern was not influenced at onset by thyroid autoimmunity, but only by metabolic derangement: pH and base excess in fact were significantly lower in patients with impaired thyroid function (p < 0.0001). Patients presenting normal thyroid function at onset showed a reduced conversion from FT4 to FT3 compared to nondiabetic children (FT3/FT4 0.3 ± 0.4 in the control group, 0.24 ± 0.4 in diabetic patients, p < 0.0001). Multiple regression analysis showed the highest correlation (negative) between FT3 levels at onset and base excess (p < 0.005). Thyroid abnormalities related to metabolic derangement disappeared during follow-up. Patients with thyroid antibodies at T1DM onset were at higher risk to require levothyroxine treatment during follow-up (p < 0.05).

CONCLUSIONS

Thyroid function at T1DM onset is mainly influenced by metabolic derangement, irrespective of thyroid autoimmunity. Antithyroid antibodies evaluation at T1DM onset may be helpful to define which patients are at higher risk of developing hypothyroidism.

Effect of tight glucose control with insulin on the thyroid axis of critically ill children and its relation with outcome

CONTEXT

Tight glucose control (TGC) to normal-for-age fasting blood glucose levels reduced morbidity and mortality in surgical adult and pediatric intensive care unit (ICU) patients. In adults, TGC did not affect the illness-induced alterations in thyroid hormones. With better feeding in children than in adult patients, we hypothesized that TGC in pediatric ICU patients reactivates the thyroid axis.

OBJECTIVE

The aim of this study was to assess the impact of TGC on the thyroid axis in pediatric ICU patients and to investigate how these changes affect the TGC outcome benefit.

DESIGN AND PATIENTS

We conducted a preplanned analysis of all patients not treated with thyroid hormone, dopamine, or corticosteroids who were included in a randomized controlled trial on TGC (n=700).

MAIN OUTCOME MEASURES

Serum TSH, T4, T3, and rT3 were measured upon admission and on ICU day 3 or the last ICU day for patients discharged earlier. Changes from baseline were compared for the TGC and usual care groups. The impact on the outcome benefit of TGC was assessed with multivariable Cox proportional hazard analysis, correcting for baseline risk factors.

RESULTS

TGC further lowered the T)/rT3 ratio (P=0.03), whereas TSH (P=0.09) and T4 (P=0.3) were unaltered. With TGC, the likelihood of earlier live discharge from the ICU was 19% higher at any time (hazard ratio, 1.190; 95% confidence interval, 1.010-1.407; P=0.03). This benefit was statistically explained by the further reduction of T3/rT3 with TGC because an increase in T3/rT3 was strongly associated with a lower likelihood for earlier live discharge (hazard ratio per unit increase, 0.863; 95% confidence interval, 0.806-0.927; P<0.0001).

CONCLUSIONS

TGC further accentuated the peripheral inactivation of thyroid hormone. This effect, mimicking a fasting response, statistically explained part of the clinical outcome benefit of TGC.

Thyroid hormone analog 3,5-diiodothyropropionic acid promotes healthy vasculature in the adult myocardium independent of thyroid effects on cardiac function

Patients with hypothyroidism are at a higher risk for coronary vascular disease. Patients with diabetes and related vascular complications also have an increased incidence of low thyroid function. While thyroid hormones (THs) may be key regulators of a healthy vasculature, potential undesirable side effects hinder their use in the treatment of vascular disorders. TH analogs such as 3,5-diiodothyropropionic acid (DITPA) may provide a safer treatment option. However, the relative potency of DITPA on vascular growth, cardiac function, and metabolism is poorly understood. We hypothesized that the vascular growth-promoting effects of DITPA can be obtained with a minimum effect on cardiac function. Thyroidectomized Sprague-Dawley rats were given slow-release pellets with either thyroxine (T4, 2.7 or 5.2 mg) or DITPA (80 mg) for 6 wk and were compared with placebo. Heart mass, body mass, body temperature, serum THs, cardiac function (echocardiograms and hemodynamics), and myocardial arteriolar density were determined. Hypothyroidism led to reductions in cardiac function, heart mass, body temperature, and myocardial arterioles. High-dose T4 prevented arteriolar loss and the development of hypothyroidism. Low-dose T4 partially prevented the reduction in cardiac function but had minimal effects on arteriolar loss. In contrast, DITPA treatment prevented myocardial arteriolar loss but not the progression of hypothyroid-induced changes in cardiac function. The results suggested that DITPA can promote a healthy vasculature independently from its thyroid-related metabolic effects. Drugs in this class may provide new therapeutic options for patients with vascular disease.

Autoimmune diseases co-occurring within individuals and within families: a systematic review

BACKGROUND

Autoimmune diseases have been observed to coexist both within individuals and within families. It is unclear whether clinical reports of comorbid autoimmune diseases represent chance findings or true associations. This systematic review evaluates the current level of evidence on the coexistence of selected autoimmune diseases within individuals and families. We reviewed the associations among 4 TH1-associated autoimmune diseases: insulin-dependent diabetes mellitus, autoimmune (Hashimoto) thyroiditis, rheumatoid arthritis, and multiple sclerosis.

METHODS

Studies quantifying the coexistence between the selected diseases, published through March 2004, were identified from Medline and Embase searches. Study eligibility was determined on the basis of preestablished criteria, and relevant data were extracted according to a fixed protocol. We determined the prevalence of comorbid autoimmune disease according to index disease and then compiled summary statistics. Heterogeneity among studies was assessed by exact likelihood ratio tests and Monte Carlo inference.

RESULTS

We found 54 studies that met the eligibility criteria. Of these, 52 studies examined the coexistence of disease within individuals and 9 studies examined within-family associations. The majority of studies were uncontrolled and did not account for confounding factors. There was substantial evidence for heterogeneity among studies. Although inconclusive, the data appear to support an increased prevalence of autoimmune thyroiditis among patients with rheumatoid arthritis and those with insulin-dependent diabetes mellitus, and an inverse association between rheumatoid arthritis and multiple sclerosis.

CONCLUSION

Although the available evidence does not permit firm conclusions regarding comorbidities among the selected autoimmune diseases, results are sufficiently suggestive to warrant further study.

TSH induces insulin receptors that mediate insulin costimulation of growth in normal human thyroid cells

The mitogenic/goitrogenic effects of thyrotropin (TSH) on human thyrocytes in vitro and in vivo depend on permissive comitogenic effects of insulin-like growth factors (IGFs), which are mimicked in vitro by the low-affinity binding of high supraphysiological concentrations of insulin to IGF-I receptors. Contrary to general assumption, we show here that very low concentrations of insulin, acting through insulin receptors but not IGF-I receptors, can also support the stimulation of DNA synthesis by TSH in primary cultures of normal human thyrocytes. Moreover, TSH through cAMP increases the content of insulin receptors demonstrated by Western blotting and the cells' responsiveness to low insulin concentrations. These observations provide the first in vitro evidence in normal human thyroid cells of a functional interaction between TSH and insulin acting through its own receptor.

High prevalence of thyroid autoantibodies at diagnosis of insulin-dependent diabetes mellitus in Swedish children

The prevalence of thyroglobulin autoantibodies and that of thyroid peroxidase autoantibodies were studied in serum samples from 52 children with insulin-dependent diabetes mellitus, sampled at diagnosis and before the start of insulin treatment, with 386 non-diabetic schoolchildren (11 to 13 years of age) serving as control subjects. Using exactly the same sensitive solid-phase immunosorbent radioassay for both thyroid autoantibodies, with comparable sensitivity, we found the prevalences of both autoantibodies to be higher in the insulin-dependent diabetes mellitus group than in the control group, the difference being most pronounced for thyroid peroxidase autoantibodies. Thyroglobulin autoantibodies were positive in 33% of the diabetics versus 14% in the control group (p = 0.002), and thyroid peroxidase autoantibodies were positive in 38% versus 6% (p = 0.0001). The high prevalence of thyroid autoantibodies already at diagnosis stresses the importance of early screening for thyroid disease in patients with insulin-dependent diabetes mellitus.

IDDM and autoimmune thyroid disease in the pediatric age group

Diabetic patients have increased chances of developing autoimmune thyroid disease. Thyroid autoantibodies (Th-AAb) are more frequent in IDDM children than in the general population, ranging between 7 and 40%. As markers of thyroid autoimmunity, we assessed Th-AAb (MsA and TgA) cross-sectionally in 212 children and adolescents (93 girls and 119 boys) aged 1.2-21 years with IDDM from 0-18 years, and longitudinally in 90/212 (43 girls and 47 boys) at diagnosis and during a 3-10 year follow-up. In the cross-sectional study Th-AAb were found in 22/93 girls (23.7%) and 13/119 boys (10.9%). In the longitudinal study Th-AAb were observed at diagnosis in 6 patients, and during the follow-up in 9 girls. In 11/15 Th-AAb positive patients anti-nuclear antibodies were also present. Hormonal assessment revealed hypothyroidism in 3 girls (afterwards on replacement therapy), thyroid ultrasonography showed abnormal patterns in 5 girls, fine needle aspiration biopsy confirmed Hashimoto's thyroiditis in 9 (8 girls and 1 boy), with a higher frequency than that reported among healthy subjects (1-2%). Thyrotoxicosis also occurs with increased frequency in diabetic children than in the general population. We observed Graves' disease in only 1/212 IDDM patients, a 13 year-old boy in whom thyrotoxicosis developed 4 years after diabetes was diagnosed. The high prevalence of thyroid autoimmunity in our patients, particularly in females, suggests that diabetic children and adolescents should be screened for thyroid autoimmunity even if asymptomatic for hypo- or hyperthyroidism. Patients with IDDM and autoimmune thyroid disease should be evaluated for autoantibodies against other organs, such as adrenal glands and gastric mucosa. It is known that patients affected by type 1 (insulin-dependent) diabetes mellitus (IDDM) may have autoantibodies against different organs, such as thyroid, adrenal glands, gastric mucosa, parathyroid, with or without evident dysfunction of the target organ /1-8/. Among organ-specific disorders, autoimmune thyroid disease (ATD) is frequently associated with IDDM and the presence of thyroid autoantibodies (Th-AAb) has been considered a risk factor for the development of hypo- or hyperthyroidism /9/.

Frequency of Hashimoto's thyroiditis in children with type 1 diabetes mellitus

A total of 1419 children with type 1 diabetes mellitus was investigated in order to assess the true frequency of Hashimoto's thyroiditis (HT), diagnosed by microsomal and/or thyroglobulin autoantibodies, by ultrasound and in many cases also by fine needle biopsy. According to these criteria, 55 cases (3.9%) of HT were identified, a number significantly higher (P < 0.0001) than the distribution reported in the normal paediatric population. No typical antibody pattern was seen prior to the onset of HT, nor was an antibody threshold level found which could have been diagnostic for this disease. Patients with subclinical hypothyroidism were treated with L-thyroxine and were investigated regarding the behaviour of anti-thyroid autoantibodies; however, no significant changes were seen. The data showed a high frequency of HT in diabetic children, and therefore we recommend that children with type 1 diabetes mellitus should be screened for thyroid autoantibodies and those positive should undergo periodic thyroid function testing.

A study of thyroid function and prevalence of thyroid autoantibodies in an African diabetic population

It is generally believed that autoimmune disorders are uncommon in Africans. Some workers have argued that insulin-dependent diabetes mellitus (IDDM) is rare in Africa on account of this reduced proneness to autoimmunity. However, it is undetermined whether or not Africans with IDDM have increased prevalence of thyroid dysfunction and autoimmunity, two phenomena strongly associated with Caucasian IDDM. We determined thyroid function and the prevalence of thyroid autoimmunity in IDDM Africans. The results are compared with those of a nondiabetic group and a group with non-insulin-dependent diabetes mellitus (NIDDM). Thyroid hormone levels were significantly lower in IDDM patients than in the control population and the NIDDM population. Subclinical hypothyroidism was present in 21% of the 28 IDDM patients. One patient was hypothyroid and another hyperthyroid. Of the 60 NIDDM patients, 5 (8.3%) had subclinical hypothyroidism. Forty-six percent of the IDDM patients had significant levels of serum thyroid autoantibodies (TAAB). This was significantly higher than the 1.4% and 1.7%, respectively, in the controls and NIDDMs. Presence of TAAB in the patients was strongly associated with thyroid dysfunction, female preponderance, and duration of diabetes mellitus. Thyroid dysfunction and autoimmunity are common in Nigerians clinically diagnosed as IDDM, and have prevalence rates comparable to other populations but higher than rates previously reported from some other African groups. The increased prevalence of thyroid autoimmunity in the IDDM supports the view that these patients are true IDDMs rather than variants of NIDDM or malnutrition-related diabetes mellitus (MRDM) as has been suggested by some workers.

Thyroid ultrasound in IDDM

Insulin dependent diabetes mellitus (IDMM) is often associated with autoimmune thyroiditis (AIT) and a high prevalence of thyroid antibodies (TA). Ultrasound imaging of the thyroid may contribute to the evaluation of patients with AIT. We therefore investigated ultrasound findings of the thyroid in 83 IDDM patients (44F, 39M) with an age range of 2.3-22.3 yrs (median 11.1). Thyroid volume (ml) determined by ultrasound ranged between 1.3 and 17.9 (median 5.7). Thyroid volumes of 75 healthy children (32F, 43M) with an age range of 2.0 to 11.8 yrs (median 7.6) ranged between 1.6 and 13.2 ml (median 4.8) and did not show a significant difference from the IDDM group from age 4 to 12. TA were positive in 18.8% of the IDDM group. Thyroid volume was higher in TA (+) diabetics (p = 0.05), a finding which may be attributed to a higher percentage of cases with elevated TSH in the TA (+) group. Two diabetic patients showed non-homogeneous hypoechogenicity in the ultrasound compatible with AIT which was later confirmed in one of these cases by aspiration biopsy. Ultrasound imaging of the thyroid may contribute to the evaluation of patients with AIT in IDDM.

Diagnostic dilemma. The goiter

The incidence of goiters in children is about 4% to 5%. The first step in the evaluation is to decide whether the swelling indeed involves the thyroid. After careful examination, one determines if the thyroid is diffusely or focally enlarged. A solitary nodule merits an extensive workup because of the high rate of malignancy. The evaluation of a diffuse goiter proceeds after deciding if the patient is euthyroid, hypothyroid, or hyperthyroid. In most cases, the child is euthyroid and the diagnosis is either CLT or simple colloid goiter. Laboratory tests for thyroid function and antibodies usually make the diagnosis. The hypothyroid patient most likely has CLT, although drugs or goitrogens, dyshormonogenesis, and thyroid resistance are also possible. The hyperthyroid patient usually has Graves' disease. The incidence of malignancy of solitary thyroid nodules is 15% to 40%; therefore, evaluation must be sensitive enough not to miss cancer. Ultrasonography helps to delineate the anatomy and to reveal if the nodule is cystic. Radionuclide scans are useful, as warm or hot lesions are rarely malignant. Cold nodules require further investigation, and in most institutions, this amounts to open biopsy. Fine-needle aspiration may be used if the clinician and pathologist are experienced. With this aggressive approach to thyroid nodules, malignancies are given early treatment. The prognosis is good in most thyroid carcinomas.

The effects of nonthyroid disease and drugs on thyroid function tests

Serious nonthyroid illness and caloric deprivation, which so often accompany systemic illness, have diverse and still incompletely understood effects on thyroid hormone economy. We have discussed the pathophysiologic basis for the most common pattern of alterations in routine thyroid function tests: a decreased serum T3 concentration; normal or, in critically ill patients, a low total serum T4 level; and a normal free T4 concentration. Another, less frequent pattern (high total and free T4 with a normal serum T3) can be encountered transiently in the acutely ill medical or psychiatric patient. With the recent advent of sensitive assays for TSH and better methods for serum free T4, it is now possible to define more quickly and accurately the thyroid-metabolic status of most of these sick patients; the vast majority are euthyroid. Certain drugs confound the picture. The most important of these include dopamine and high-dose glucocorticoids, both of which suppress TSH secretion from the pituitary and may actually cause a state of central hypothyroidism. Other drugs have multiple effects on thyroid hormone indices (e.g., amiodarone). Knowledge of all of the ways in which systemic illness, starvation, and certain drugs may influence thyroid function tests is crucial in assessing the thyroid status of patients with serious nonthyroid disease.