In Kallmann syndrome, which physical characteristic is notably absent?

In Kallmann syndrome, the notably absent physical characteristic is the sense of smell. This condition is characterized by a combination of hypogonadism and anosmia, which is the loss of the sense of smell. Kallmann syndrome arises from a failure of the olfactory bulbs and the hypothalamus to develop normally, which results in the absence of olfactory bulbs leading to anosmia. Additionally, this condition is associated with a deficiency in the production of gonadotropin-releasing hormone (GnRH), leading to reduced levels of sex hormones and associated symptoms.

The other senses—taste, sight, and touch—are typically not impaired in individuals with Kallmann syndrome, making the dysfunction of the olfactory system the hallmark of this condition. This highlights the unique connection between anosmia and the reproductive deficiencies observed in this syndrome.