Hormone Glossary

Depression

DHT (dihydrotestosterone)

Diagnostic Test

Disorder

Domino Effect

Dopamine

Dopamine is an excitatory and inhibitory neurotransmitter, depending on the dopaminergic receptor it binds to. It is derived from the amino acid tyrosine. Dopamine is the precursor to norepinephrine and epinephrine, which are all catecholamines. The function of dopamine is diverse but plays a large role in the pleasure/reward pathway (addiction and thrills), memory, and motor control. Dopamine, like norepinephrine and epinephrine, is stored in vesicles in the axon terminal. Dopamine plays a significant role in the cardiovascular, renal, hormonal, and central nervous systems. The dopaminergic neurons have dendrites that extend into various regions of the brain, controlling different functions through the stimulation of adrenergic and dopaminergic receptors (D1 –D5). Common symptoms with low dopamine levels are loss of motor control, addictions, cravings, compulsions, and loss of satisfaction. When dopamine levels are elevated symptoms may manifest in the form of anxiety or hyperactivity. Some therapies utilize L-DOPA for parkinsonian symptoms which can also cause elevations in dopamine.

Dopamine Metabolite

After neuronal dopamine is released it is inactivated primarily via reuptake mechanisms that remove it from the synapse and the extraneuronal space and return it to the presynaptic dopaminergic neuron or adjacent noradrenergic neurons. Some of the enzymes that degrade dopamine are only found in specific regions of the body. As such some dopamine metabolites are only produced in specific tissues. Understanding how and where these enzymes function can provide valuable insight about how dopamine is functioning in specific regions of the body. In order to understand these functions one must first realize Monoamine oxidase (MAO) is an enzyme present within the cytoplasm of neurons that breaks down dopamine to DOPAL. DOPAL in turn is very rapidly converted to DOPAC by a second cytoplasmic enzyme aldehyde dehydrogenase (AD). Because both of these enzymes are primarily found inside neurons, DOPAC levels are dependent on the amount of cytoplasmic dopamine. Combined measurements of DOPAC and dopamine have been used to assess the activity of dopaminergic neurons. This combination provides additional information than either parameter alone because a large portion of DOPAC is formed from dopamine without ever being released to the synaptic cleft. This suggests that DOPAC may be more closely related to the presynaptic dopamine levels while dopamine and similarly HVA levels, another important metabolite of dopamine that is formed outside of the neuron via the actions of catechols-O-methyltransferase (COMT), are related to the rate of neuron signaling. Said another way, extracellular DOPAC is related to the amount of dopamine made and stored in the presynaptic neuron while extracellular dopamine levels are related to the rate of dopamine released via the depolarization of dopamine neurons.

Dosage

Double blind

Endometriosis

Environmental Factors

Epinephrine

Epinephrine, also known as adrenaline, is an excitatory neurotransmitter and hormone essential for lipolysis, which is a process in which the body metabolizes fat. Epinephrine is derived from the amine norepinephrine. As a neurotransmitter, epinephrine regulates attentiveness and mental focus. Epinephrine is synthesized from norepinephrine.As a hormone, epinephrine is secreted along with norepinephrine principally by the medulla of the adrenal gland. Heightened secretion can occur in response to fear or anger and will result in increased heart rate and the hydrolysis of glycogen to glucose. This reaction, referred to as the “fight or flight” response, prepares the body for strenuous activity. Epinephrine is used medicinally as a stimulant in cardiac arrest, as a vasoconstrictor in shock, as a bronchodilator and antispasmodic in bronchial asthma, and anaphylaxis. Commonly, epinephrine levels will be low due to adrenal fatigue (a pattern in which the adrenal output is suppressed due to chronic stress). Therefore, symptoms can be presented as fatigue with low epinephrine levels. Low levels of epinephrine can also contribute to weight gain and poor concentration. Elevated levels of epinephrine can be factors contributing to restlessness, anxiety, sleep problems, or acute stress.

Erectile Dysfunction

Estradiol

Estriol

Estrogen

Estrogen Dominance

Estrone

Fatigue

Fibroids