Hypothalamic–pituitary–thyroid axis and TSH receptor antibodies may be the reason for the observation that the relation between free T4 concentration and TSH levels deviates from a pure loglinear relation that has previously been proposed. Standard procedures cover the determination of serum levels of the following hormones: For special conditions the following assays and procedures may be required: Hypothalamic–pituitary–thyroid axis The hypothalamic–pituitary–thyroid axis (HPT axis for short, a.k.a. thyroid homeostasis or thyrotropic feedback control) is part of the neuroendocrine system responsible for the regulation of metabolism. As its name suggests, it depends upon the hypothalamus, the pituitary gland, and the thyroid gland. The
Releasing and inhibiting hormones response to low levels of secretion of thyroid-stimulating hormone (TSH) from the pituitary gland. The TSH in turn is under feedback control by the thyroid hormones T4 and T3. When the level of TSH is too high, they feed back on the brain to shut down the secretion of TRH. Synthetic TRH is also used by physicians as a test of TSH reserve in the pituitary gland as it should stimulate the release of TSH and prolactin from this gland. The main releasing hormones are as follows: The main release-inhibiting hormones or inhibiting hormones are as follows: There are various