PARATHYROID GLAND

PARATHYROID GLAND:

 

http://www.parathyroid.com/images/pth.gif

o  There are 4 parathyroid glands in humans

o    They are located immediately behind the thyroid gland

o    Each gland is about 6mm long, 3mm wide and 2mm thick.

o  It secretes parathormone (PTH) or Para thyroid hormone

Parathyroid Hormone Or Parathormone

Chemistry

ü PTH is a linear polypeptide with 84 amino acids.

ü Has 9500 Daltons mol. weight.

ü N-terminal of PTH is Alanine

C-terminal of PTH is Glutamine

Synthesis

ü PTH is synthesized in chief cells of Parathyroid gland.

ü Initially it is synthesized as Pre Pro PTH with 115 amino acids from Polysomes adhered on RER.

ü Before the formation of complete Pre Pro PTH, the N-terminal end protruding from lumen of ER is cleaved by signal peptidase hydrolyzing 25 amino acid and leaving Pro PTH with 90 amino acids.

ü Pro PTH from ER moves to Golgi where Clipase enzyme cleaves 6 amino acid, thus converting Pro PTH to PTH with 84 amino acids.

http://www.nbs.csudh.edu/chemistry/faculty/nsturm/CHE452/images/PTHProcessing.gif

Secretion

Ø Increased c AMP concentration and decreased Ca2+ level stimulate its release from vesicles.

Ø Normal concentration in Blood   is 8 to 51Pg/ml

Functions of PTH

Ø Increases Ca2+ concentration in serum by

o  Increasing Ca2+ absorption from intestine

o  Decreasing Ca2+ excretion in Urine.

o  Removing Ca from bones, particularly if dietary intake of Ca is inadequate.

Ø PTH also increases Phosphate concentration in blood.

Ø PTH helps in the activation of Osteoclasts.

 Regulation of PTH secretion:

http://www.endocrinesurgeon.co.uk/images/stories/content/pth-cycle.jpg

 

 

 

 

 

Comments

Post a Comment

Popular posts from this blog

THYROID GLAND

Image
THYROID GLAND o   Thyroid Gland is located immediately below the larynx on its either side and anterior to trachea. o   It weighs about 15-20gms o   Thyroid gland has number of follicles filled with colloid and lined by Cuboid epithelial cells. o   The major component of colloid is a large glycoprotein Thyroglobulin which contains the thyroid hormones within it. o   Thyroid gland secretes 2 major hormones Ø   Tetra-Iodo Thyronine(or) Thyroxine (or) T4 Ø   Tri-Iodo Thyronine(or)T3 THYROID HORMONES o   The principle hormones secreted by the follicular epithelial cells are T3 and T4 o   About 93% of metabolically active hormones secreted by thyroid gland is T4 and 7% are T3. o   T3 is more potent than T4 o   T3 has short half-life than T4 Chemistry o   Both Thyroxine and Tri Iodo thyronine are formed from Tyrosine of Thyroglobulin by Iodination. T3 (Tri Iodo thyronine) o   Molecular weight -65...
Read more

Ovarian cycle and its regulation.

  The ovarian cycle has follicular (FSH, estrogen), ovulation (LH flow), and luteal (progesterone) phases, regulated by the hypothalamic–pituitary–ovarian axis through a delicate balance of feedback mechanisms. 1. Ovarian Cycle – Phases The ovarian cycle lasts about 28 days (average) and has three main phases: A. Follicular Phase (Day 1–14, variable) Begins with menstruation . FSH stimulates growth of several ovarian follicles. One follicle becomes dominant (Graafian follicle) → secretes estrogen . Rising estrogen → proliferation of endometrium (preparing for implantation). B. Ovulation (Around Day 14) High estrogen levels (positive feedback) → LH surge . LH surge causes: Final maturation of oocyte. Rupture of Graafian follicle → release of ovum. C. Luteal Phase (Day 15–28, fixed ~14 days) Remaining follicle forms corpus luteum . Corpus luteum secretes progesterone (main) + estrogen . Progesterone prepares endometrium (se...
Read more

Chemistry, Secretion, Functions and Regulations of Gonadal hormones: Testosterone

Image
Testosterone – Chemistry, Secretion, Functions, and Regulation 1. Chemistry Testosterone is a steroid hormone. It belongs to the group of androgens (male sex hormones). Derived from cholesterol in the Leydig cells of testes. It is lipid-soluble and easily passes through cell membranes. 2. Site of Secretion Males: Mainly secreted by Leydig (interstitial) cells in testes. Females: Secreted in very small amounts by the ovaries and adrenal cortex. In blood, testosterone is mostly bound to sex hormone-binding globulin (SHBG) and albumin; only 2–3% is free and biologically active. 3. Normal Secretion In Males: Average adult production: 6–7 mg/day. Blood levels: about 300–1000 ng/dL. Secretion starts during fetal life (for male sex differentiation), decreases after birth, rises again at puberty, and gradually declines after 40–50 years (andropause). In Females: Much lower levels (20–70 ng/dL). Contributes to libido, bone health, and muscle strength. 4. Functions of Testosterone ✅ ...
Read more