Irisin as a regulator of bone and glucose metabolism

[helvella]

Just what does any endocrinologist really know about hormones?

Do they even know of the existence of half of them?

No, of course I am not saying that they should know about things that have not been discovered. But they just might accept that:

There are more things in heaven and earth, Horatio,

Than are dreamt of in your philosophy.

shakespeare-online.com/quic...

(No, I don't know of any endos called Horatio. )

The paper mentions "fat browning". There are two sorts of fat cell - white and brown. Brown fat cells are associated with things like producing heat without shivering.

In many animals, brown and white fat cells are very obvious and distinct. In humans, it appears that they co-exist and the fat cell areas can become more white, or more brown.

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Minerva Endocrinol. 2018 Dec;43(4):489-500. doi: 10.23736/S0391-1977.17.02779-1. Epub 2017 Nov 20.

Irisin as a regulator of bone and glucose metabolism.

Briganti SI1, Gaspa G2, Tabacco G1, Naciu AM1, Cesareo R3, Manfrini S1, Palermo A4.

Author information

1 Unit of Endocrinology and Diabetes, Department of Medicine, Campus Bio-Medico University, Rome, Italy.

2 Department of Food Science and Nutrition, Campus Bio-Medico University, Rome, Italy.

3 Thyroid and Osteometabolic Disease Center, S. Maria Goretti Hospital, Latina, Italy.

4 Unit of Endocrinology and Diabetes, Department of Medicine, Campus Bio-Medico University, Rome, Italy - [e-mail].

Abstract

In humans, irisin is produced mainly by skeletal muscle in response to physical activity. It has been demonstrated that irisin plays a pivotal role in inducing fat browning and regulating energy expenditure. New findings from various studies conducted in both animals and humans suggest that irisin can affect bone and glucose metabolism. In particular, irisin is able to increase bone cortical mass by stimulating the osteoblast pathways, and irisin levels are inversely correlated with the incidence of fragility fractures among postmenopausal women affected by osteoporosis. Most available evidence shows that irisin significantly influences glucose and energy homeostasis. Indeed, higher irisin concentrations are inversely correlated with type 2 diabetes. Unfortunately, contradictory findings exist concerning the role of irisin in humans, and most of the human studies that have analyzed interactions between bone health, glucose metabolism, and irisin have several limitations; therefore, their results must be interpreted with caution. The purpose of this narrative review is mainly to describe the effects of irisin on glucose and bone metabolism.

PMID: 29160051

DOI: 10.23736/S0391-1977.17.02779-1

ncbi.nlm.nih.gov/pubmed/291...

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J Int Med Res. 2019 Feb 6:300060518824445. doi: 10.1177/0300060518824445. [Epub ahead of print]

Role of irisin in Chinese patients with hypothyroidism: an interventional study.

Yang N1, Zhang H1, Gao X1, Miao L1, Yao Z1, Xu Y1, Wang G1.

Author information

1 1 Department of Endocrinology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.

Abstract

OBJECTIVE:

Irisin is a myokine that greatly affects energy expenditure and systemic metabolism. While thyroid hormone is likely associated with irisin, a direct relationship remains to be fully elucidated. This study aimed to investigate plasma irisin levels in Chinese patients with hypothyroidism.

METHODS:

A total of 155 subjects were divided into the hypothyroidism group or the control group. Fifty-seven patients in the hypothyroidism group received levothyroxine treatment. Baseline irisin levels were measured in the two groups and post-treatment levels were measured in the hypothyroidism group.

RESULTS:

Irisin levels were significantly lower in the hypothyroidism group than in the control group. In the hypothyroidism group, irisin levels were positively associated with free triiodothyronine and free thyroxine levels, and negatively associated with thyrotropin levels. In the hypothyroidism group, irisin levels were significantly increased after levothyroxine treatment. Multiple linear regression models showed that total cholesterol and free thyroxine levels were the only significant predictors of serum irisin levels.

CONCLUSIONS:

Irisin levels are decreased in patients with hypothyroidism. Our results suggest that decreased irisin levels are directly associated with reduced thyroid hormone levels. These values may be restored after levothyroxine treatment in Chinese patients with hypothyroidism.

KEYWORDS:

Irisin; creatine kinase; hypothyroidism; levothyroxine; myokine; thyroid hormone

PMID: 30722716

DOI: 10.1177/0300060518824445

ncbi.nlm.nih.gov/pubmed/307...

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J Endocrinol Invest. 2019 Feb;42(2):175-181. doi: 10.1007/s40618-018-0899-8. Epub 2018 May 18.

Irisin levels increase after treatment in patients with newly diagnosed Hashimoto thyroiditis.

Uc ZA1, Gorar S2, Mizrak S3, Gullu S4.

Author information

1 Department of Endocrinology, Usak University School of Medicine, Usak, Turkey. [e-mail].

2 Department of Endocrinology, Antalya Training and Research Hospital, Antalya, Turkey.

3 Department of Biochemistry, Usak University School of Medicine, Usak, Turkey.

4 Department of Endocrinology, Ankara University School of Medicine, Ankara, Turkey.

Abstract

PURPOSE:

Irisin is a newly identified myokine secreted by skeletal muscle and has significant effects on body metabolism. Thyroidal functional state has a profound influence on the metabolism of human body. Therefore, the aim of this study was to investigate the possible changes in serum irisin concentrations before and after treatment in hypothyroid subjects.

METHODS:

The study included 26 patients with overt hypothyroidism due to Hashimoto thyroiditis and 19 healthy subjects. Baseline serum thyroid function tests and presence of thyroid autoantibodies and levels of creatine kinase (CK) and irisin were measured in both groups. All measurements in the hypothyroid group were repeated after euthyroidism was achieved.

RESULTS:

Serum irisin levels were significantly lower in the hypothyroid groups than the control group (p < 0.001). Negative correlation between irisin and thyroid stimulating hormone and CK levels (r = - 0.623, p < 0.001 and r = - 0.389, p = 0.008, respectively) and a positive correlation between irisin and free thyroxine (fT4) levels (r = 0.570, p < 0.001) was found. Serum CK levels decreased significantly after treatment (p < 0.001). Serum irisin levels significantly increased (from 57.4 to 99.8 U/L, p < 0.001) when the hypothyroid patients were treated to achieve euthyroidism.

CONCLUSIONS:

To the best of our knowledge, this is the first study providing insight that low serum irisin levels significantly increased following treatment to euthyroid state in overt hypothyroid patients with Hashimoto thyroiditis. Larger scale studies are needed to confirm these results and to ensure irisin as a possible biomarker of Hashimoto's thyroiditis.

KEYWORDS:

Hashimoto thyroiditis; Hypothyroidism; Irisin; Overt hypothyroidism

PMID: 29777516

DOI: 10.1007/s40618-018-0899-8

ncbi.nlm.nih.gov/pubmed/297...

[TSH110]

Thanks for posting with pertinent bard quote 😊

I wonder how thyroid hormone combination therapy affects the levels compared to monotherapy

[helvella Administrator in reply to TSH110]

Well, I suspect that conversion efficiency is an important element. I was pleased that one of the quoted papers says: ...irisin levels were positively associated with free triiodothyronine and free thyroxine levels

[Angel_of_the_North]

Wonder how it correlates with free t3? you'd expect positively, but that's not necessarily true

[helvella Administrator in reply to Angel_of_the_North]

I think some of us have been around long enough to realise that almost nothing in the thyroid world is obvious. It is rife with assumptions, many of which are later shown to be falsely based.