DƯỢC LÍ Goodman & Gilman's The Pharmacological Basis of Therapeutics 12th, 2010

Table 38–2
Properties of the Protein Hormones of the Human Adenohypophysis and Placenta
MASS PEPTIDE AMINO ACID CHROMOSOMAL
HORMONE (daltons) CHAINS RESIDUES LOCATION COMMENTS
Somatotropic hormones
Growth hormone (GH) 22,000 1 191 17q22-24
Prolactin (PRL) 23,000 1 199 6p22.2-21.3
Placental lactogen (PL) 22,125 1 190 17q22-24
Glycoprotein hormones
Luteinizing hormone (LH) 29,400 2 α-92 6q12.q21 Heterodimeric glycoproβ-121
19q13.3 teins with a common
Follicle-stimulating 32,600 2 α-92 6q12.q21 α-subunit and unique
hormone (FSH) β-111 11p13 β-subunits that deter-
Human chorionic 38,600 2 α-92 6q12.q21 mine biological
gonadotropin (hCG) β-145 19q13.3 specificity
Thyroid-stimulating 28,000 2 α-92 6q12.q21
hormone (TSH) β-118 1p13
POMC-derived hormones*
Corticotropin (ACTH) 4500 1 39 2p22.3 These peptides are derived
α-Melanocyte-stimulating 1650 1 13 by proteolytic hormone
(α-MSH)
processing of the
common precursor,
pro-opiomelanocortin
(POMC)
*See Chapter 42 for further discussion of POMC-derived peptides, including ACTH and α-MSH.
hormone (GHRH), gonadotropin-releasing hormone
(GnRH), and thyrotropin-releasing hormone (TRH).
Somatostatin (SST), another hypothalamic peptide,
negatively regulates secretion of pituitary GH and TSH.
The neurotransmitter dopamine inhibits the secretion
of prolactin by lactotropes.
The posterior pituitary gland, also known as the
neurohypophysis, contains the endings of nerve axons
arising from distinct populations of neurons in the
supraoptic and paraventicular nuclei of the hypothalamus
that synthesize either arginine vasopressin or
oxytocin (Figure 38–1). Arginine vasopressin plays an
important role in water homeostasis (Chapter 25);
oxytocin plays important roles in labor and parturition
and in milk letdown, as discussed in the following
sections and in Chapter 66.
SOMATOTROPIC HORMONES: GROWTH
HORMONE AND PROLACTIN
GH and prolactin are structurally related members of
the somatotropic hormone family and share many
biological features, thus providing a rationale for discussing
them together. The somatotropes and lactotropes,
the pituitary cells that produce GH and
prolactin, respectively, derive during pituitary development
from a common precursor and are eosinophilic in
histological sections. Consistent with their common origin,
defects in certain transcription factors affect both
cell lineages. In addition to their structural similarities,
GH and prolactin act via membrane receptors that
belong to the cytokine receptor family and modulate
target cell function via very similar signal transduction
pathways (Chapter 3). The secretion of both hormones
is subject to strong inhibitory input from hypothalamic
neurons; for prolactin, this negative dopaminergic input
clearly is the predominant regulator of secretion.
Finally, several drugs that are used to treat excessive
secretion of these hormones are effective to varying
degrees for both GH and prolactin.
Physiology of the Somatotropic Hormones
Structures of the Somatotropic Hormones. The gene
encoding human GH resides on the long arm of