Thyrotropin blood levels, subclinical hypothyroidism, and the elderly patient

Multiple hormonal dysregulation as determinant of low physical performance and mobility in older persons

Mobility-disability is a common condition in older individuals. Many factors, including the age-related hormonal dysregulation, may concur to the development of disability in the elderly. In fact, during the aging process it is observed an imbalance between anabolic hormones that decrease (testosterone, dehydroepiandrosterone sulphate (DHEAS), estradiol, insulin like growth factor-1 (IGF-1) and Vitamin D) and catabolic hormones (cortisol, thyroid hormones) that increase. We start this review focusing on the mechanisms by which anabolic and catabolic hormones may affect physical performance and mobility. To address the role of the hormonal dysregulation to mobility-disability, we start to discuss the contribution of the single hormonal derangement. The studies used in this review were selected according to the period of time of publication, ranging from 2002 to 2013, and the age of the participants (≥65 years). We devoted particular attention to the effects of anabolic hormones (DHEAS, testosterone, estradiol, Vitamin D and IGF-1) on both skeletal muscle mass and strength, as well as other objective indicators of physical performance. We also analyzed the reasons beyond the inconclusive data coming from RCTs using sex hormones, thyroid hormones, and vitamin D (dosage, duration of treatment, baseline hormonal values and reached hormonal levels). We finally hypothesized that the parallel decline of anabolic hormones has a higher impact than a single hormonal derangement on adverse mobility outcomes in older population. Given the multifactorial origin of low mobility, we underlined the need of future synergistic optional treatments (micronutrients and exercise) to improve the effectiveness of hormonal treatment and to safely ameliorate the anabolic hormonal status and mobility in older individuals.

Treatment with thyroid hormone

Thyroid hormone deficiency can have important repercussions. Treatment with thyroid hormone in replacement doses is essential in patients with hypothyroidism. In this review, we critically discuss the thyroid hormone formulations that are available and approaches to correct replacement therapy with thyroid hormone in primary and central hypothyroidism in different periods of life such as pregnancy, birth, infancy, childhood, and adolescence as well as in adult patients, the elderly, and in patients with comorbidities. Despite the frequent and long term use of l-T4, several studies have documented frequent under- and overtreatment during replacement therapy in hypothyroid patients. We assess the factors determining l-T4 requirements (sex, age, gender, menstrual status, body weight, and lean body mass), the major causes of failure to achieve optimal serum TSH levels in undertreated patients (poor patient compliance, timing of l-T4 administration, interferences with absorption, gastrointestinal diseases, and drugs), and the adverse consequences of unintentional TSH suppression in overtreated patients. Opinions differ regarding the treatment of mild thyroid hormone deficiency, and we examine the recent evidence favoring treatment of this condition. New data suggesting that combined therapy with T3 and T4 could be indicated in some patients with hypothyroidism are assessed, and the indications for TSH suppression with l-T4 in patients with euthyroid multinodular goiter and in those with differentiated thyroid cancer are reviewed. Lastly, we address the potential use of thyroid hormones or their analogs in obese patients and in severe cardiac diseases, dyslipidemia, and nonthyroidal illnesses.

Is subclinical hypothyroidism a cardiovascular risk factor in the elderly?

CONTEXT

The negative impact of subclinical hypothyroidism (sHT) on cardiovascular risk, widely recognized in young adults (aged <55-60 y), is still debated in the elderly (>65 y), especially in the oldest olds (>80 y).

EVIDENCE ACQUISITION

We searched Medline for reports published with the following search terms: "hypothyroidism," "subclinical hypothyroidism," "ageing," "elderly," "L-thyroxin," "thyroid," "guidelines," "treatment," "quality of life," "cardiovascular risk," "heart failure," "coronary heart disease" (CHD), "atherosclerosis," and "endothelial dysfunction." We limited our search to reports in English published after 1980, although we incorporated some reports published before 1980. We supplemented the search with records from personal files, textbooks, and relevant articles. Analyzed parameters included the epidemiology of thyroid failure, the effect of thyroid hormone on the aging process, cardiovascular function, and CHD risk factors. We also included the potential benefits of L-T4 therapy on the quality of life, cardiovascular events, and survival.

EVIDENCE SYNTHESIS

TSH levels increase with age, even in older people without thyroid disease. Most longitudinal studies show an increased risk for CHD events and mortality in sHT participants. This increase is less evident in the elderly, mainly in cases of serum TSH values above 10 mIU/L. Lower mortality rate in a cohort of the oldest olds (>85 y) has been reported.

CONCLUSIONS

sHT in older people should be not regarded as a unique condition, and moderately old patients (aged <70-75 y) could be considered clinically similar to the adult population, albeit with a higher optimal TSH target value. Conversely, the oldest old subjects should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. The decision to treat elderly people is still an unresolved clinical challenge--first, due to a lack of appropriately powered randomized controlled trials of L-T4 in sHT patients, examining cardiovascular hard endpoints in various classes of age; and second, because of the negative effects of possible overtreatment.

Subclinical thyroid dysfunction and cognitive decline in old age

Background

Subclinical thyroid dysfunction has been implicated as a risk factor for cognitive decline in old age, but results are inconsistent. We investigated the association between subclinical thyroid dysfunction and cognitive decline in the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER).

Methods

Prospective longitudinal study of men and women aged 70–82 years with pre-existing vascular disease or more than one risk factor to develop this condition (N = 5,154). Participants taking antithyroid medications, thyroid hormone supplementation and/or amiodarone were excluded. Thyroid function was measured at baseline: subclinical hyper- and hypothyroidism were defined as thyroid stimulating hormones (TSH) <0.45 mU/L or >4.50 mU/L respectively, with normal levels of free thyroxine (FT4). Cognitive performance was tested at baseline and at four subsequent time points during a mean follow-up of 3 years, using five neuropsychological performance tests.

Results

Subclinical hyperthyroidism and hypothyroidism were found in 65 and 161 participants, respectively. We found no consistent association of subclinical hyper- or hypothyroidism with altered cognitive performance compared to euthyroid participants on the individual cognitive tests. Similarly, there was no association with rate of cognitive decline during follow-up.

Conclusion

We found no consistent evidence that subclinical hyper- or hypothyroidism contribute to cognitive impairment or decline in old age. Although our data are not in support of treatment of subclinical thyroid dysfunction to prevent cognitive dysfunction in later life, only large randomized controlled trials can provide definitive evidence.

The incidence of thyroid function abnormalities and natural course of subclinical thyroid disorders, Tehran, I.R. Iran

BACKGROUND

Despite the high prevalence of thyroid dysfunction, the epidemiology and natural course of these disorders have not been identified yet.

AIM

The present survey was conducted to determine the incidence of thyroid dysfunction and natural course of subclinical thyroid disorders in an urban community of Tehran, I.R. Iran.

SUBJECTS AND METHODS

Serum TSH and thyroperoxidase antibody (TPOAb) were measured at baseline and after 6.7 yr from a sample of 1999 randomly selected subjects aged≥20 yr, participants of the Tehran Lipid and Glucose Study (TLGS). Median TSH value and 2.5, 5, 95, and 97.5 TSH percentiles were determined at baseline using data obtained from 808 negative TPOAb subjects with no history of any thyroid disease or surgery, goiter, nodule, taking thyroid hormone preparations or anti-thyroid drugs. In those with abnormal TSH level, total T4 and T3 uptake were measured and free T4 index was calculated.

RESULTS

Normal TSH reference range was 0.4-5.8 μU/ml according to the 2.5 and 97.5 TSH percentiles. The incidence rates of thyroid function abnormalities in 1000 subjects per year were as follows: clinical hypothyroidism: 0.28 in women and 0.21 in men; subclinical hypothyroidism: 11.59 in women and 4.69 in men; clinical hyperthyroidism: 1.4 in women and 0.21 in men; and subclinical hyperthyroidism: 5.72 in women and 3.62 in men. A significant increase was found in the frequency of positive TPOAb in women from 15.9 to 17.7% (p=0.006). Of 8 women with subclinical hypothyroidism at baseline, 5 remained unchanged, 1 became normal, and 1 developed clinical hypothyroidism at followup. Two women with subclinical hyperthyroidism normalized at follow-up. Of 2 men with subclinical hypothyroidism at baseline, 1 remained unchanged, whereas the other progressed to clinical hypothyroidism.

CONCLUSION

After a 6.7 yr follow-up significant increase in the incidence of subclinical thyroid disorders was observed in both men and women, as compared to overt thyroid dysfunction. Increase in the prevalence of TPOAb positivity was observed only in women.

Thyroid disease in older people

Several changes in thyroid hormone secretion, metabolism, and action occur with the increase in age. Aging is often associated with a decrease in serum thyroid stimulating hormone and T3 levels, whereas serum free T4 levels usually remain unchanged. The prevalence of thyroid dysfunction is higher in the elderly as compared to the younger population. In elderly individuals the non-specific clinical manifestations of thyroid hormone excess or deprivation can cause confusion in the clinical setup; while some of the symptoms of thyroid disease are similar to those in younger patients, it is not uncommon for both hyperthyroidism and hypothyroidism to be manifested in subtle ways in older patients, often mimicking symptoms of aging or masquerading as diseases of the cardiovascular, gastrointestinal, or nervous system. In addition, diagnosis of thyroid disorders is commonly complicated, due to chronic, non-thyroidal illness or medication therapy. Early diagnosis and treatment of overt thyroid disorders is crucial, since these disorders are associated with increased morbidity and mortality in the elderly, usually due to common coexistent diseases such as diminished cardiovascular reserve. Treatment of subclinical thyroid disease should also be considered, based on a combination of age, symptoms and risk factors in the individual patients. In addition, both prevalence and aggressiveness of thyroid cancer increase with age. This review summarizes the changes of thyroid function, as well as the clinical manifestations and treatment of thyroid disorders with advancing age.