Role of endocrine glands in regulation of body functions

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Role of endocrine glands in regulation of body
functions

• Author
• ass.prof. N.M. Volkova

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• The thyroid gland contains spherical follicles
  (50500 µmin diameter).
• Follicle cells synthesize the two
  iodine-containing thyroid hormones thyroxine (T4,
  tetraiodothyronine) and triiodothyronine (T3).

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• Thyroid hormone activation of target cells

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Thyroid hormone activation oftarget 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.

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Regulation of thyroid secretion
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Iodine metabolism

• Iodine circulates in the blood as either (1)
  inorganic I (210 µg/L), (2) organic
  non-hormonal iodine (traces) and (3)
  protein-bound iodine (PBI) within T3 and T4
  (3580 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).

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The Menstrual Cycle

• The first day of menses is day 1 of the menstrual
  cycle, and menses typically lasts 45 days.
• Ovulation occurs on about day 14 of a 28-day
  menstrual cycle, although the timing of ovulation
  varies.

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Factors That Influence the Process of Parturition
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Hormonal Control of Lactation
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Menopause

• When a female is 4050 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.

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