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Conrad Hoffmann, Eberhard Spoerl; The Effect of Hypothyroidism on Mechanical and Biochemical Properties of the Cornea. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3719.
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To examine the effect of hypothyroidism on mechanical and biochemical properties of the cornea.
Hypothyroidism was induced in 20 male Wistar rats by administering 6-n-propyl-2-thiouracil (PTU) in their drinking water for 8 weeks at a concentration of 0.05%. 20 euthyroid rats were used as controls. Animals were sacrificed and cardiocentesis was done to quantify fT3 and TSH blood levels. Afterwards central corneal thickness (CCT) was measured (TOMEY Pachymeter SP 3000). Then enucleation of both eyes was performed. One complete cornea of each rat was used for photometric determination of the glycosaminoglycan-levels (GAG) using a DMMB-Assay. The second cornea of each rat was cut into a longitudinal stripe and subjected to various preselected levels of stress in a uniaxial tensile-testing device.
After 8 weeks of treatment with PTU a significant hypothyroidism was induced (0.535 vs. 4.484 pmol/l; P<0.001). Analysis of stress-strain curves disclosed no significant differences between the two groups (p=0,4). But CCT was significantly reduced in hypothyroid rats (159 vs. 176 µm; P=0.001). Also concentration of GAG was reduced in the group of hypothyroid rats (1.49 vs. 1.66 µg/mg).
Hypothyroidism is assumed to be a risk factor to develop keratoconus. Treatment with PTU due to the above mentioned procedure leads to significant hypothyroidism. In our study we could not find significant changes in corneal stiffness of hypothyroid rats but statistically significant corneal thinning and reduction of GAG level, leading to the assumption that there is an association between hypothyroidism and keratoconus.
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