Understanding the Healthy Thyroid State in 2015

Abstract

Thyroid hormones (TH) are of crucial importance for the physiological function of almost all organs. In cases of abnormal TH signaling, pathophysiological consequences may arise. The routine assessment of a healthy or diseased thyroid function state is currently based on the determination of serum concentrations of thyroid-stimulating hormone (TSH), and the TH T₃ and T₄. However, the definition of a ‘normal' TSH range and similarly ‘normal' T₃ and T₄ concentrations remains the subject of debate in different countries worldwide and has important implications on patient treatment in clinics. Not surprisingly, a significant number of patients whose thyroid function tests are biochemically determined to be within the normal range complain of impaired well-being. The reasons for this are so far not fully understood, but it has been recognized that thyroid function status needs to be ‘individualized' and extended beyond simple TSH measurement. Thus, more precise and reliable parameters are required in order to optimally define the healthy thyroid status of an individual, and as a perspective to employ these in clinical routine. With the recent identification of new key players in TH action, a more accurate assessment of a patient's thyroid status may in the future become possible. Recently described distinct TH derivatives and metabolites, TH transporters, nongenomic TH effects (either through membrane-bound or cytosolic signaling), and classical nuclear TH action allow for insights into molecular and cellular preconditions of a healthy thyroid state. This will be a prerequisite to improve management of thyroid dysfunction, and additionally to prevent and target TH-related nonthyroid disease.

A family with hypothyroidism caused by fatty acid synthase and apolipoprotein B receptor mutations

“…Generally, hypothyroidism is diagnosed either in the subclinical or clinical form. Congenital hypothyroidism, if not treated, may lead to severe and irreversible mental retardation ( 6 ).…”

Age- and Gender-Specific Changes in Thyroid Size and Thyroid Function Test Values of Euthyroid Subjects

“…Thyroid hormones (TH) play the important role in the development and the maintenance of homeostasis through the interactions with autonomic nervous system and the regulations of cardiovascular and metabolic functions [1] [2].…”

Characterization of the human thyroid epigenome

“…The thyroid gland produces and secretes hormones necessary for growth and development and is involved with the regulation of metabolism. Assessment of thyroid function is based on blood serum concentrations of thyroid-related hormones (thyroid-stimulating hormone (TSH), triiodothyronine (T3) or thyroxine (T4)) in predefined normal ranges (Führer et al 2015). However, the definition of a 'normal' TSH, T3 and T4 concentration range is controversial (Führer et al 2015) when variability in individual factors such as sex, body mass index, exclusion of incident thyroid disease, ethnicity and iodine and selenium intake are considered.…”

“…Assessment of thyroid function is based on blood serum concentrations of thyroid-related hormones (thyroid-stimulating hormone (TSH), triiodothyronine (T3) or thyroxine (T4)) in predefined normal ranges (Führer et al 2015). However, the definition of a 'normal' TSH, T3 and T4 concentration range is controversial (Führer et al 2015) when variability in individual factors such as sex, body mass index, exclusion of incident thyroid disease, ethnicity and iodine and selenium intake are considered. Furthermore, thyroid nodules are common, diagnosed in 5% of the general population by palpation and in 50% by ultrasound (Gharib & Papini 2007) suggesting frequent local heterogeneity within thyroid glands.…”