Sorted By Test Name - Mayo Medical Laboratories

HTTO
60339
(SSRIs) Evaluating patients with treatment-resistant depression Predicting response time to improvement
with SSRIs Identifying patients who might respond favorably to a class of antidepressants other than
SSRI. Identifying patients who have diminished amounts of the serotonin transporter and, hence, an
altered response to SSRI therapeutics
Interpretation: The normal (wildtype) allele yields a long product (l/l). The variant is short/short (s/s).
Heterozygotes have a l/s genotype. Individuals homozygous for the long allele (l/l) may respond more
rapidly to selective serotonin reuptake inhibitors (SSRI) therapy. Individuals homozygous for the short
allele (s/s) may respond more slowly to SSRI therapy and may benefit from a longer trial before
considering switching to another antidepressant. Even 1 copy of the short allele (heterozygous) decreases
the amount of the transporter protein present, increasing the time to response.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Lesch KP, Gutnecht L: Pharmacogenetics of the serotonin transporter. Prog
Neuropsychopharmacol Biol Psychiatry 2005;29:1062-1073 2. Genecard at NCBI for 5-HTT. XenneX,
Inc. 2005 October 18; Retrieved 1/06; Available from URL:
http://www.genecards.org/cgi-bin/carddisp?SLC6A4&snpcount=49 3. Serretti A, Kato M, De Ronchi D,
Kinoshita T: Meta-analysis of serotonin transporter gene promoter polymorphisms (5-HTTLPR)
associated with selective serotonin reuptake inhibitor efficacy in depressed patients. Mol Psych
2007;12:247-257
Serotonin Transporter Genotype, Saliva
Clinical Information: Serotonin (5-hydroxytryptamine; 5-HT) is a neurotransmitter. The serotonin
transporter (5-HTT) modulates neurotransmission by facilitating removal of serotonin from the synapse of
serotonergic neurons, resulting in serotonin reuptake into the presynaptic terminus. Other designations for
5-HTT are SLC6A4 (solute carrier family 6 [neurotransmitter transporter, serotonin], member 4), hSERT,
OCD1, SERT, sodium-dependent serotonin transporter, and 5-HT transporter. Selective serotonin
reuptake inhibitors (SSRIs) block the action of the serotonin transporter and are used to treat depression
and other neuropsychiatric disorders. Examples of SSRIs include fluoxetine (Prozac), fluvoxamine
(Luvox), escitalopram oxalate (Lexapro), sertraline (Zoloft), citalopram (Celexa), and paroxetine (Paxil,
Paxil CR). The 5-HTT gene is located at 17q11.1-q12 and is composed of 14 exons spanning 31 kb. A
44-base pair promoter insertion/deletion polymorphism called LPR, or linked polymorphic region,
produces alleles described as long or short. The short allele is dominant and results in decreased
concentration of the transporter protein and a poorer response to stressful events. While individuals
homozygous for the long allele (l/l) may demonstrate response to SSRI therapy in 3 to 4 weeks,
individuals with the short allele (l/s or s/s) may respond to SSRI therapy more slowly, taking up to 12
weeks.
Useful For: Qualifying participants for clinical trials Evaluating patients who have failed therapy with
selective serotonin reuptake inhibitors (SSRIs) Evaluating patients with treatment-resistant depression
Predicting response time to improvement with SSRIs Identifying patients who might respond favorably to
nonselective antidepressants Identifying patients who have diminished amounts of the serotonin
transporter and, hence, an altered response to SSRI therapeutics
Interpretation: The normal (wildtype) allele yields a long product (l/l). The variant is short/short (s/s).
Heterozygotes have a l/s genotype. Individuals homozygous for the long allele (l/l) may respond more
rapidly to selective serotonin reuptake inhibitor (SSRI) therapy. Individuals homozygous for the short
allele (s/s) may respond more slowly to SSRI therapy and may benefit from a longer trial before
considering switching to another antidepressant. Even 1 copy of the short allele (heterozygous) decreases
the amount of the transporter protein present, increasing the time to response.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Lesch KP, Gutnecht L: Pharmacogenetics of the serotonin transporter. Prog
Neuropsychopharmacol Biol Psychiatry 2005;29:1062-1073 2. Genecard at NCBI for 5-HTT. XenneX,
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