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Recently, the biological sensors based on surface plasmon resonance (SPR) have been highly investigated due to their versatile application in the field of medicine and pharmacy. In this study, we introduce a Kretschmann based sensor including a BK7 prism, gold, Pb5Ge3O11 (PGO) and graphene layers. The special optical properties of the ferroelectric PGO layer plays a key role on improving the sensor performance. Initially the sensing sample is considered to be water where the sensor is sensitive to the refractive index changes of the sensing medium, Δn=0.005 (RIU), connected to outer layer. The structure sensitivity and the figure of merit (FOM) obtained as 228.22 (Deg/RIU) and 22.36 (1/RIU) at the wavelength of 632.8nm, respectively, which are higher than conventional structures properties. The main goal of the introduced sensor is to detect hypothyroidism caused by deficiency of thyroid hormones that is directly related to lack of hemoglobin level in the human body. According to the relationship between hemoglobin concentration and refractive index of blood, the sensor can be used to diagnostic tool. Also, by replacing blood profile of healthy people and patients into sensor structure some characteristics such as FWHM and reflectivity is obtained. Eventually, any impairment in refractive index of blood due to disease is recognizable with this group of sensors. For example, the achieved FWHM and reflectivity are 10.4308 (Deg) and 0.4739 (a.u) for healthy people and 10.3862 (Deg) and 0.4482 (a.u) for patients, respectively.
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