Research Information System
Thesis Type: Expertise In Medicine
Institution Of The Thesis: Gazi Üniversitesi, Tıp Fakültesi, Turkey
Approval Date: 2014
Student: YUSUF TOHMA
Supervisor: MÜJDE YAŞIM AKTÜRK
Abstract:Hyperthyroidism is associated with increased appetite but also with weight loss, however the responsible mechanisms are not conclusively clarified. Hyperthyroid patients are characterized by increased appetite, but also they have increased basal metabolic rate and energy expenditure thus resulting in weight loss. We aimed to investigate the association between appetite related hormones; nesfatin- 1, orexin-A, neuropeptide Y, Agouti related peptide levels and daily food intake, basal metabolic rate, body composition measurements in hyperthyroidism. The study group included 21 patients with overt hyperthyroidism and 33 healthy euthyroid volunteers well matched for sex, age and BMI. The patient group was assessed before treatment and in averagely 10,2 months after treatment when euthyrodism is achieved. In order to measure basal metabolic rate, we used maksimum O2 uptake capacity (VO2). 24-hour dietary recalls were recorded and computer assisted programmes were used to estimate daily food intake. Blood orexin-A, nesfatin-1, neuropeptide Y and AgRP levels were measured using ELISA method. Patients with overt hyperthyroidism had higher basal metabolic rate than healthy controls. In the hypertyhroid group, food intake decreased and BMI increased when patients achieved euthyroidism. In the overt hyperthyroidism group, orexin-A levels were significantly lower than healthy controls which were similar to healthy controls when patients achieved euthyroidism. In the overt hyperthyroidism group, nesfatin-1 levels were significantly higher than in healthy controls which decreased significantly and were similar to healthy controls when euthyroidism was achieved. There was no statistically significant difference in NPY and AgRP levels between healthy controls and patient group, neither in euthyroid nor hyperthyroid state. We observed that hyperthyroidic state is an independent predictive of orexin-A levels, while orexin-A level is predictive for basal metabolic rate. We discovered that hyperthyroidism is related with blood nesfatin-1 and orexin-A levels. We found lower orexigenic peptid orexin-A levels and higher anorexigenic peptid nesfatin-1 levels in hyperthyroid patients than healthy controls, which suggests a compensation since hyperthyroid patients have increased appetite already. Therefore other mechanisms may be responsible for the increased appetite in hyperthyroidism. There are several studies reporting nesfatin-1 and orexin-A levels are altered in mood disorders, supraventricular tachycardia, sleep disturbances, thermogenesis which are also observed in hyperthyroidism, suggesting that nesfatin-1 and orexin-A have more comprehensive effects than being solely anorexigenic and orexigenic peptides. In our study, high levels of nesfatin-1 and low levels of orexin-A in hyperthyroid patients may be associated with these systematic disturbances in hyperthyroidism. The role of appetite related hormones in hyperthyroidism remains to be a subject of discussion. Therefore further studies which evaluate peripheral and central levels of these peptides are necessary to clarify the relationship between thyroid hormones and energy metabolism.