Examining the relationship between non-alcoholic fatty liver disease and hypothyroidism

One of the most prevalent endocrine system disorders with lifetime repercussions on health is hypothyroidism. Due to inadequate thyroid secretion, this illness results in thyroid dysfunction. One of the common liver ailments, non-alcoholic fatty liver disease (NAFLD), denotes the buildup of fat in the liver without consuming alcohol. NAFLD and hypothyroidism frequently coexist, and the development of NAFLD may be influenced by the condition. Teimouri K, Pakravan S, Azadbakht K. Examining the relationship between non-alcoholic fatty liver disease and hypothyroidism. J Parathyr Dis. 2022;10:e9148. Copyright is an open-access the terms


Introduction
The liver is a crucial organ for the body's various physiological functions, including the regulation of blood volume, immune system function, fat and cholesterol balance, and the metabolism of macronutrients )1(. Protein synthesis and the metabolism of several hormones both depend on the liver. As a result, several endocrine abnormalities are linked to liver ailments )2(. The largest gland in the body, the liver is primarily in charge of the environmental conversion of tetraiodothyronine )T4( to triiodothyronine )T3(, which is a crucial step in the metabolism of thyroid hormones )3(. Thyroid hormones )T3 and T4( are responsible for regulating various functions of the body, including the metabolism of lipids and carbohydrates, oxygen consumption, and some physiological functions such as reproduction and growth )4(. The rate of metabolism of liver cells is regulated by thyroxine and triiodothyronine. On the contrary, thyroid hormone metabolism occurs in the liver, which also controls the systemic effects of these hormones. As a result, liver disease may interfere with the metabolism of thyroid hormones whereas thyroid dysfunction may affect liver function )5(. One of the most prevalent chronic liver illnesses is a non-alcoholic fatty liver disease )NAFLD( )6(. Thyroid dysfunction, especially hypothyroidism, has been associated with it )7(, It has been shown that decreased thyroid hormone concentrations may cause hyperlipidemia and obesity, thereby causative to NAFLD )8(. Despite the exact physiological mechanism of NAFLD development, the correlation between NAFLD and hypothyroidism is unclear )9(. In the current study, we investigate the association between NAFLD and hypothyroidism.

Materials and Methods
In this article, we review recently published works that inspect the correlation between NAFLD and hypothyroidism. Articles were searched in PubMed, Google Scholar, and ScienceDirect databases with related keywords such as thyroid gland, liver, non-alcoholic fatty liver disease, and hypothyroidism.

Hypothyroidism
Failure of the thyroid gland is referred to as hypothyroidism; it is more common in women than in males and gets worse with age )10(. The inability of the thyroid gland to produce enough thyroid hormone to satisfy the body's metabolic requirements is known as hypothyroidism. Thyroid-stimulating hormone levels rise and blood T4 and T3 levels fall in the clinical hypothyroidism )11(.

Non-alcoholic fatty liver disease
It is known as NAFLD when there is no alcohol consumption and fat build up in liver cells )12(. The NAFLD affects more than a quarter of adults worldwide )13(. NAFLD is a term for a variety of illnesses, such as nonalcoholic simple fatty liver disease )NASFL(, nonalcoholic steatohepatitis, liver cirrhosis, and hepatocellular carcinoma. NAFLD is a more common cause of liver cirrhosis and is also one of the main causes of liver cancer )14(. Several extrahepatic organ systems are affected by the multisystem illness known as NAFLD )6(.

Conclusion
The current investigation revealed a link between NAFLD and hypothyroidism. The importance of early risk patient identification stems from the fact that treatment of hypothyroidism may lower the risk of NAFLD and its possible consequences. It is yet unclear how NAFLD and hormonal problems are related. Endocrinologists frequently ignore NAFLD, and hepatologists are the only ones who assess it. NAFLD has a long-term clinical impact, so endocrinologists and hepatologists need to be aware of its variations linked to endocrine disorders.

Conflicts of interest
There are no conflicts of interest declared by the authors.

Ethical issues
Ethical concerns (including plagiarism, data fabrication, and double publication) are fully respected by the authors.

Funding/Support
No financing from any source.