Download 1.7 Role of endocrine glands in regulation of body functions

Role of endocrine glands in
regulation of body functions
Author
ass.prof. N.M. Volkova
• The thyroid gland contains spherical follicles
(50–500 μmin diameter).
• Follicle cells synthesize the two iodinecontaining thyroid hormones thyroxine (T4,
tetraiodothyronine) and triiodothyronine (T3).
• Thyroid
hormone
activation
of target
cells
Thyroid hormone activation of
target cells
• Thyroxine (T4) and triiodothyronine (T3) readily
diffuse through the cell membrane.
• Much of the T4 is deiodinated to form T3, which
interacts with the thyroid hormone receptor,
bound as a heterodimer with a retinoid X
receptor, of the thyroid hormone response
element of the gene.
• This causes either increases or decreases in
transcription of genes that lead to formation of
proteins, thus producing the thyroid hormone
response of the cell.
Regulation of thyroid secretion
Iodine metabolism
• Iodine circulates in the blood as either (1)
inorganic I– (2–10 μg/L), (2) organic nonhormonal iodine (traces) and (3) protein-bound
iodine (PBI) within T3 and T4 (35–80 μg
iodine/L). The average daily requirement of
iodine is ca. 150 μg.
• Iodine excreted from the body must be replaced
by the diet.
• Since iodine passes into the breast milk,
nursingmothers have a higher daily requirement
of iodine (ca. 200 μg/day).
The Menstrual
Cycle
• The first day of
menses is day 1
of the menstrual
cycle, and
menses typically
lasts 4–5 days.
• Ovulation occurs
on about day 14
of a 28-day
menstrual cycle,
although the
timing of
ovulation varies.
Factors That Influence the Process
of Parturition
Hormonal Control of Lactation
Menopause
• When a female is 40–50 years old, menstrual
cycles become less regular, and ovulation often
does not occur. Eventually menstrual cycles stop
completely.
• The cessation of menstrual cycles is called
menopause. The time from the onset of irregular
cycles to their complete cessation, which is often
3 to 5 years, is called the female climacteric or
perimenopause.
• A variety of symptoms occur in some females
during the climacteric, including “hot flashes,”
irritability, fatigue, anxiety, and occasionally
severe emotional disturbances.