Luteinizing Hormone: Structure, Function and Related Problems With This Hormone

This hormone controls to a great extent the reproductive system of the human body.

With different roles in the bodies of men and women, this important hormone is crucial to ensure a healthy reproductive system. Taking control of your reproductive health requires understanding this essential hormone.

Luteinizing hormone (LH) is produced and released in the anterior pituitary gland . This hormone is considered a gonadotropic hormone because of its role in controlling the function of the ovaries in women and the testes in men, which are known as the gonads.

Structure

Luteinizing hormone is a heterodimeric glycoprotein. Each monomer unit is a glycoprotein molecule; an alpha subunit and a beta make up the complete functional protein.

Its structure is similar to that of the other glycoprotein hormones, follicle-stimulating hormone (FSH), thyroid stimulating hormone (TSH) and human chorionic gonadotropin (hCG).

The protein dimer contains 2 glycopeptide subunits, labeled alpha and beta subunits, which are non-covalently associated (ie, without any disulfide bridge linking them)

Function

In women, the hormone stimulates the ovaries to produce estradiol. Two weeks after the start of a woman’s cycle, an increase in luteinizing hormone causes the ovaries to release an egg during ovulation.

If fertilization occurs, luteinizing hormone will stimulate the corpus luteum, which produces progesterone to maintain pregnancy.

For men, luteinizing hormone stimulates the production of testosterone from the Leydig cells in the testes. Testosterone, in turn, stimulates sperm production and helps accentuate male characteristics, such as a deep voice or the growth of facial hair.

What problems can occur with luteinizing hormone?

People who have high levels of luteinizing hormone may experience infertility, because the hormone directly affects the reproductive system.

In women, luteinizing hormone levels that are too high are often connected with polycystic ovarian syndrome , which creates inappropriate levels of testosterone.

Some genetic conditions, such as Turner syndrome or Klinefelter syndrome, can also cause elevated hormone levels. People with these conditions often can not reproduce.

Low levels of luteinizing hormone can also cause infertility, because insufficient levels will limit sperm production or the ovulation process.

Very little luteinizing hormone stops ovulation in women or creates a deficiency in the secretion of gonadotropin-releasing hormone (GnRH) in men.

Excess of luteinizing hormone

In children with precocious puberty of pituitary or central origin, the levels of LH and FSH may be in the reproductive range instead of the typical low levels for their age.

During the reproductive years, relatively high luteinizing hormone is frequently observed in patients with polycystic ovarian syndrome; however, it would be unusual for them to have LH levels outside the normal reproductive range.

The persistently high levels of luteinizing hormone are indicative of situations in which the normal restrictive feedback of the gonad is absent, leading to a pituitary production of LH and FSH. While this is typical at menopause, it is abnormal in the reproductive years. There may be a sign of:

  • Premature menopause
  • Gonadal dysgenesis, Turner syndrome.
  • Castration.
  • Swyer syndrome.
  • Polygamistic Ovary Syndrome.
  • Certain forms of congenital adrenal hyperplasia.
  • Testicular failure
  • Pregnancy: BetaHCG can simulate LH, so the tests can show an elevation of LH.

Note: A medical drug to inhibit the secretion of luteinizing hormone is butinazocine.

Deficiency of luteinizing hormone

The decrease in the secretion of luteinizing hormone can cause the failure of gonadal function ( hypogonadism ).

This condition usually manifests itself in men as a failure in the production of normal numbers of sperm. In women, amenorrhea is commonly observed. Conditions with very low luteinizing hormone secretions include:

  • Pasqualini’s syndrome.
  • Síndrome de Kallmann.
  • Hypothalamic suppression.
  • Hipopituitarismo.
  • Eating disorder.
  • Triad of female athlete.
  • Hyperprolactinemia
  • Hipogonadismo.
  • Gonadal suppression therapy.
  • GnRH antagonist.
  • GnRH agonist (which induces an initial stimulation followed by permanent blockade of the pituitary GnRH receptor).