Consequences of undertreatment of hypothyroidism

Abstract

Purpose: To provide an overview of consequences of undertreatment with levothyroxine (LT4) in the common non-communicable disease, hypothyroidism.

Methods: Narrative review of the literature.

Results: Hypothyroidism is globally very prevalent at all age groups and represents a non-communicable disease in which the risks and consequences are preventable. In children and adolescents, the most devastating consequences of undertreatment are poor growth and development. Lack of early treatment in congenital hypothyroidism can lead to permanent damage of brain function. In young to middle-aged adults, consequences are often overlooked, and treatment delayed by many years. The resulting consequences are also at this age group compromised brain and physical functioning but less severe and partly reversible with treatment. The undertreated condition often results in a higher risk of several secondary devastating diseases such as increased cardiovascular disease burden, obesity, hypertension, poor physical capacity, poor quality of life. In young women of fertile age the consequences of undertreatment with LT4 are subnormal fertility, recurrent pregnancy loss, preeclampsia, compromised fetal growth and neurocognitive development. There is a further risk of 30-50% of developing postpartum thyroiditis. In the elderly population care must be given to avoid confusing a slightly high serum TSH as result of physiological age adaptation with a requirement for LT4 treatment in a truly hypothyroid patient.

Conclusion: Undertreatment of the preventable non-communicable disease hypothyroidism requires more focus both from caretakers in the healthcare system, but also from the global political systems in order to prevent the personally devastating and socioeconomically challenging consequences.

Keywords: Age; Levothyroxine; Optimisation; Thyroid function; Treatment.

Fig. 1

Overview of thyroid hormone actions. Thyroid hormone production and secretion are regulated by a negative feedback mechanism with the hypothalamus producing thyrotropin releasing hormone in response to low concentrations of T3 and T4, which again stimulate the anterior pituitary to produce and secrete TSH, resulting in stimulation of the thyroid gland to increase T3 and T4 production. The far majority of thyroid hormones are circulated in the blood stream bound to proteins until reaching target organs. Alb albumin, T3 triiodothyronine, T4 thyroxine, TBG thyroid binding globulin, TH thyroid hormone, THR thyroid hormone receptor, TRH thyrotropin releasing hormone, TSH thyroid stimulating hormone. Created with BioRender.com