Why would a tumor on the pituitary gland affect the thyroid gland and also tims levels of testosterone

Pituitary gland is the master gland of the body that controls all other glands and their secretions. Since, the pituitary decides which gland produces what amount of a hormone, a tumor on the pituitary will affect the way these glands secrete their hormones.

Explanation:

Pituitary Gland:

The master gland, located in the brain that controls the hormone secretions of all other glands of the body. Just as the hypothalamus acts as a thermostat to detect any changes in body temperature, the pituitary senses the levels of particular hormones in the blood. Then, based on these levels and the bodily needs, the pituitary signals glands to increase or decrease their secretions.

Pituitary Tumor:

A pituitary tumor is an undifferentiated, uncontrolled growth on the pituitary gland. Pituitary tumors are mostly benign. They are of two types:

Functioning Tumors are ones that produce hormones on their own. They exhibit symptoms. Non-functioning tumor do not produce hormones. They do not display symptoms. A functioning tumor will produce high amounts of thyroid stimulating hormone (TSH) that stimulates the thyroid gland to produce more thyroxine hormones (T3 and T4). This condition is termed hyperthyroidism. Similarly, testosterone levels may decrease due to high production of prolactin by prolactin secreting tumors on the pituitary. This condition is termed hypogonadism (suppression of gonads). Although, gonadotropin secreting tumors are mostly non-functioning, in rare cases, they can cause an increase in testosterone levels.