<prompt> Testotoxicosis is due toGain of function mutation of Gs aLoss of function mutation of Gs aBoth gain and loss of function mutation of Gs aMutation in Gs a resulting in decrease in intrinsic GTPase activity  <response>: Testotoxicosis is an interesting disease that combines gain and loss of function. In this condition, an activating mutation of Gs a causes excess testosterone secretion and prepubeal sexual maturation. However, this mutation is temperature-sensitive and is active only at the relatively low temperature of the testes 33 degC. At 37 degC, the normal temperature of the rest of the body, it is replaced by loss of function, with the production of hypoparathyroidism and decreased responsiveness to TSH. 